NAME
    ossl-guide-migration, migration_guide - OpenSSL Guide: Migrating from
    older OpenSSL versions

SYNOPSIS
    See the individual manual pages for details.

DESCRIPTION
    This guide details the changes required to migrate to new versions of
    OpenSSL. Currently this covers OpenSSL 3.0 & 3.1. For earlier versions
    refer to <https://github.com/openssl/openssl/blob/master/CHANGES.md>.
    For an overview of some of the key concepts introduced in OpenSSL 3.0
    see crypto(7).

OPENSSL 3.1
  Main Changes from OpenSSL 3.0
    The FIPS provider in OpenSSL 3.1 includes some non-FIPS validated
    algorithms, consequently the property query "fips=yes" is mandatory for
    applications that want to operate in a FIPS approved manner. The
    algorithms are:

    Triple DES ECB
    Triple DES CBC
    EdDSA

    There are no other changes requiring additional migration measures since
    OpenSSL 3.0.

OPENSSL 3.0
  Main Changes from OpenSSL 1.1.1
   Major Release
    OpenSSL 3.0 is a major release and consequently any application that
    currently uses an older version of OpenSSL will at the very least need
    to be recompiled in order to work with the new version. It is the
    intention that the large majority of applications will work unchanged
    with OpenSSL 3.0 if those applications previously worked with OpenSSL
    1.1.1. However this is not guaranteed and some changes may be required
    in some cases. Changes may also be required if applications need to take
    advantage of some of the new features available in OpenSSL 3.0 such as
    the availability of the FIPS module.

   License Change
    In previous versions, OpenSSL was licensed under the dual OpenSSL and
    SSLeay licenses
    <https://www.openssl.org/source/license-openssl-ssleay.txt> (both
    licenses apply). From OpenSSL 3.0 this is replaced by the Apache License
    v2 <https://www.openssl.org/source/apache-license-2.0.txt>.

   Providers and FIPS support
    One of the key changes from OpenSSL 1.1.1 is the introduction of the
    Provider concept. Providers collect together and make available
    algorithm implementations. With OpenSSL 3.0 it is possible to specify,
    either programmatically or via a config file, which providers you want
    to use for any given application. OpenSSL 3.0 comes with 5 different
    providers as standard. Over time third parties may distribute additional
    providers that can be plugged into OpenSSL. All algorithm
    implementations available via providers are accessed through the "high
    level" APIs (for example those functions prefixed with "EVP"). They
    cannot be accessed using the "Low Level APIs".

    One of the standard providers available is the FIPS provider. This makes
    available FIPS validated cryptographic algorithms. The FIPS provider is
    disabled by default and needs to be enabled explicitly at configuration
    time using the "enable-fips" option. If it is enabled, the FIPS provider
    gets built and installed in addition to the other standard providers. No
    separate installation procedure is necessary. There is however a
    dedicated "install_fips" make target, which serves the special purpose
    of installing only the FIPS provider into an existing OpenSSL
    installation.

    Not all algorithms may be available for the application at a particular
    moment. If the application code uses any digest or cipher algorithm via
    the EVP interface, the application should verify the result of the
    EVP_EncryptInit(3), EVP_EncryptInit_ex(3), and EVP_DigestInit(3)
    functions. In case when the requested algorithm is not available, these
    functions will fail.

    See also "Legacy Algorithms" for information on the legacy provider.

    See also "Completing the installation of the FIPS Module" and "Using the
    FIPS Module in applications".

   Low Level APIs
    OpenSSL has historically provided two sets of APIs for invoking
    cryptographic algorithms: the "high level" APIs (such as the "EVP" APIs)
    and the "low level" APIs. The high level APIs are typically designed to
    work across all algorithm types. The "low level" APIs are targeted at a
    specific algorithm implementation. For example, the EVP APIs provide the
    functions EVP_EncryptInit_ex(3), EVP_EncryptUpdate(3) and
    EVP_EncryptFinal(3) to perform symmetric encryption. Those functions can
    be used with the algorithms AES, CHACHA, 3DES etc. On the other hand, to
    do AES encryption using the low level APIs you would have to call AES
    specific functions such as AES_set_encrypt_key(3), AES_encrypt(3), and
    so on. The functions for 3DES are different. Use of the low level APIs
    has been informally discouraged by the OpenSSL development team for a
    long time. However in OpenSSL 3.0 this is made more formal. All such low
    level APIs have been deprecated. You may still use them in your
    applications, but you may start to see deprecation warnings during
    compilation (dependent on compiler support for this). Deprecated APIs
    may be removed from future versions of OpenSSL so you are strongly
    encouraged to update your code to use the high level APIs instead.

    This is described in more detail in "Deprecation of Low Level Functions"

   Legacy Algorithms
    Some cryptographic algorithms such as MD2 and DES that were available
    via the EVP APIs are now considered legacy and their use is strongly
    discouraged. These legacy EVP algorithms are still available in OpenSSL
    3.0 but not by default. If you want to use them then you must load the
    legacy provider. This can be as simple as a config file change, or can
    be done programmatically. See OSSL_PROVIDER-legacy(7) for a complete
    list of algorithms. Applications using the EVP APIs to access these
    algorithms should instead use more modern algorithms. If that is not
    possible then these applications should ensure that the legacy provider
    has been loaded. This can be achieved either programmatically or via
    configuration. See crypto(7) man page for more information about
    providers.

   Engines and "METHOD" APIs
    The refactoring to support Providers conflicts internally with the APIs
    used to support engines, including the ENGINE API and any function that
    creates or modifies custom "METHODS" (for example EVP_MD_meth_new(3),
    EVP_CIPHER_meth_new(3), EVP_PKEY_meth_new(3), RSA_meth_new(3),
    EC_KEY_METHOD_new(3), etc.). These functions are being deprecated in
    OpenSSL 3.0, and users of these APIs should know that their use can
    likely bypass provider selection and configuration, with unintended
    consequences. This is particularly relevant for applications written to
    use the OpenSSL 3.0 FIPS module, as detailed below. Authors and
    maintainers of external engines are strongly encouraged to refactor
    their code transforming engines into providers using the new Provider
    API and avoiding deprecated methods.

   Support of legacy engines
    If openssl is not built without engine support or deprecated API
    support, engines will still work. However, their applicability will be
    limited.

    New algorithms provided via engines will still work.

    Engine-backed keys can be loaded via custom OSSL_STORE implementation.
    In this case the EVP_PKEY objects created via ENGINE_load_private_key(3)
    will be considered legacy and will continue to work.

    To ensure the future compatibility, the engines should be turned to
    providers. To prefer the provider-based hardware offload, you can
    specify the default properties to prefer your provider.

    Setting engine-based or application-based default low-level crypto
    method such as RSA_METHOD or EC_KEY_METHOD is still possible and keys
    inside the default provider will use the engine-based implementation for
    the crypto operations. However EVP_PKEYs created by decoding by using
    OSSL_DECODER, PEM_ or d2i_ APIs will be provider-based. To create a
    fully legacy EVP_PKEYs EVP_PKEY_set1_RSA(3), EVP_PKEY_set1_EC_KEY(3) or
    similar functions must be used.

   Versioning Scheme
    The OpenSSL versioning scheme has changed with the OpenSSL 3.0 release.
    The new versioning scheme has this format:

    MAJOR.MINOR.PATCH

    For OpenSSL 1.1.1 and below, different patch levels were indicated by a
    letter at the end of the release version number. This will no longer be
    used and instead the patch level is indicated by the final number in the
    version. A change in the second (MINOR) number indicates that new
    features may have been added. OpenSSL versions with the same major
    number are API and ABI compatible. If the major number changes then API
    and ABI compatibility is not guaranteed.

    For more information, see OpenSSL_version(3).

   Other major new features
   Certificate Management Protocol (CMP, RFC 9810)
    This also covers CRMF (RFC 4211) and HTTP transfer (RFC 9811) See
    openssl-cmp(1) and OSSL_CMP_exec_certreq(3) as starting points.

   HTTP(S) client
    A proper HTTP(S) client that supports GET and POST, redirection, plain
    and ASN.1-encoded contents, proxies, and timeouts.

   Key Derivation Function API (EVP_KDF)
    This simplifies the process of adding new KDF and PRF implementations.

    Previously KDF algorithms had been shoe-horned into using the EVP_PKEY
    object which was not a logical mapping. Existing applications that use
    KDF algorithms using EVP_PKEY (scrypt, TLS1 PRF and HKDF) may be slower
    as they use an EVP_KDF bridge internally. All new applications should
    use the new EVP_KDF(3) interface. See also "Key Derivation Function
    (KDF)" in OSSL_PROVIDER-default(7) and "Key Derivation Function (KDF)"
    in OSSL_PROVIDER-FIPS(7).

   Message Authentication Code API (EVP_MAC)
    This simplifies the process of adding MAC implementations.

    This includes a generic EVP_PKEY to EVP_MAC bridge, to facilitate the
    continued use of MACs through raw private keys in functionality such as
    EVP_DigestSign(3) and EVP_DigestVerify(3).

    All new applications should use the new EVP_MAC(3) interface. See also
    "Message Authentication Code (MAC)" in OSSL_PROVIDER-default(7) and
    "Message Authentication Code (MAC)" in OSSL_PROVIDER-FIPS(7).

   Algorithm Fetching
    Using calls to convenience functions such as EVP_sha256() and
    EVP_aes_256_gcm() may incur a performance penalty when using providers.
    Retrieving algorithms from providers involves searching for an algorithm
    by name. This is much slower than directly accessing a method table. It
    is recommended to prefetch algorithms if an algorithm is used many
    times. See "Performance" in crypto(7), "Explicit fetching" in crypto(7)
    and "Implicit fetching" in crypto(7).

   Support for Linux Kernel TLS
    In order to use KTLS, support for it must be compiled in using the
    "enable-ktls" configuration option. It must also be enabled at run time
    using the SSL_OP_ENABLE_KTLS option.

   New Algorithms
    *   KDF algorithms "SINGLE STEP" and "SSH"

        See EVP_KDF-SS(7) and EVP_KDF-SSHKDF(7)

    *   MAC Algorithms "GMAC" and "KMAC"

        See EVP_MAC-GMAC(7) and EVP_MAC-KMAC(7).

    *   KEM Algorithm "RSASVE"

        See EVP_KEM-RSA(7).

    *   Cipher Algorithm "AES-SIV"

        See "SIV Mode" in EVP_EncryptInit(3).

    *   AES Key Wrap inverse ciphers supported by EVP layer.

        The inverse ciphers use AES decryption for wrapping, and AES
        encryption for unwrapping. The algorithms are: "AES-128-WRAP-INV",
        "AES-192-WRAP-INV", "AES-256-WRAP-INV", "AES-128-WRAP-PAD-INV",
        "AES-192-WRAP-PAD-INV" and "AES-256-WRAP-PAD-INV".

    *   CTS ciphers added to EVP layer.

        The algorithms are "AES-128-CBC-CTS", "AES-192-CBC-CTS",
        "AES-256-CBC-CTS", "CAMELLIA-128-CBC-CTS", "CAMELLIA-192-CBC-CTS"
        and "CAMELLIA-256-CBC-CTS". CS1, CS2 and CS3 variants are supported.

   CMS and PKCS#7 updates
    *   Added CAdES-BES signature verification support.

    *   Added CAdES-BES signature scheme and attributes support (RFC 5126)
        to CMS API.

    *   Added AuthEnvelopedData content type structure (RFC 5083) using
        AES_GCM

        This uses the AES-GCM parameter (RFC 5084) for the Cryptographic
        Message Syntax. Its purpose is to support encryption and decryption
        of a digital envelope that is both authenticated and encrypted using
        AES GCM mode.

    *   PKCS7_get_octet_string(3) and PKCS7_type_is_other(3) were made
        public.

   PKCS#12 API updates
    The default algorithms for pkcs12 creation with the PKCS12_create()
    function were changed to more modern PBKDF2 and AES based algorithms.
    The default MAC iteration count was changed to PKCS12_DEFAULT_ITER to
    make it equal with the password-based encryption iteration count. The
    default digest algorithm for the MAC computation was changed to SHA-256.
    The pkcs12 application now supports -legacy option that restores the
    previous default algorithms to support interoperability with legacy
    systems.

    Added enhanced PKCS#12 APIs which accept a library context OSSL_LIB_CTX
    and (where relevant) a property query. Other APIs which handle PKCS#7
    and PKCS#8 objects have also been enhanced where required. This
    includes:

    PKCS12_add_key_ex(3), PKCS12_add_safe_ex(3), PKCS12_add_safes_ex(3),
    PKCS12_create_ex(3), PKCS12_decrypt_skey_ex(3), PKCS12_init_ex(3),
    PKCS12_item_decrypt_d2i_ex(3), PKCS12_item_i2d_encrypt_ex(3),
    PKCS12_key_gen_asc_ex(3), PKCS12_key_gen_uni_ex(3),
    PKCS12_key_gen_utf8_ex(3), PKCS12_pack_p7encdata_ex(3),
    PKCS12_pbe_crypt_ex(3), PKCS12_PBE_keyivgen_ex(3),
    PKCS12_SAFEBAG_create_pkcs8_encrypt_ex(3), PKCS5_pbe2_set_iv_ex(3),
    PKCS5_pbe_set0_algor_ex(3), PKCS5_pbe_set_ex(3), PKCS5_pbkdf2_set_ex(3),
    PKCS5_v2_PBE_keyivgen_ex(3), PKCS5_v2_scrypt_keyivgen_ex(3),
    PKCS8_decrypt_ex(3), PKCS8_encrypt_ex(3), PKCS8_set0_pbe_ex(3).

    As part of this change the EVP_PBE_xxx APIs can also accept a library
    context and property query and will call an extended version of the
    key/IV derivation function which supports these parameters. This
    includes EVP_PBE_CipherInit_ex(3), EVP_PBE_find_ex(3) and
    EVP_PBE_scrypt_ex(3).

   PKCS#12 KDF versus FIPS
    Unlike in 1.x.y, the PKCS12KDF algorithm used when a PKCS#12 structure
    is created with a MAC that does not work with the FIPS provider as the
    PKCS12KDF is not a FIPS approvable mechanism.

    See EVP_KDF-PKCS12KDF(7), PKCS12_create(3), openssl-pkcs12(1),
    OSSL_PROVIDER-FIPS(7).

   Windows thread synchronization changes
    Windows thread synchronization uses read/write primitives (SRWLock) when
    supported by the OS, otherwise CriticalSection continues to be used.

   Trace API
    A new generic trace API has been added which provides support for
    enabling instrumentation through trace output. This feature is mainly
    intended as an aid for developers and is disabled by default. To utilize
    it, OpenSSL needs to be configured with the "enable-trace" option.

    If the tracing API is enabled, the application can activate trace output
    by registering BIOs as trace channels for a number of tracing and
    debugging categories. See OSSL_trace_enabled(3).

   Key validation updates
    EVP_PKEY_public_check(3) and EVP_PKEY_param_check(3) now work for more
    key types. This includes RSA, DSA, ED25519, X25519, ED448 and X448.
    Previously (in 1.1.1) they would return -2. For key types that do not
    have parameters EVP_PKEY_param_check(3) will always return 1.

   Other notable deprecations and changes
   The function code part of an OpenSSL error code is no longer relevant
    This code is now always set to zero. Related functions are deprecated.

   STACK and HASH macros have been cleaned up
    The type-safe wrappers are declared everywhere and implemented once. See
    DEFINE_STACK_OF(3) and DEFINE_LHASH_OF_EX(3).

   The RAND_DRBG subsystem has been removed
    The new EVP_RAND(3) is a partial replacement: the DRBG callback
    framework is absent. The RAND_DRBG API did not fit well into the new
    provider concept as implemented by EVP_RAND and EVP_RAND_CTX.

   Removed FIPS_mode() and FIPS_mode_set()
    These functions are legacy APIs that are not applicable to the new
    provider model. Applications should instead use
    EVP_default_properties_is_fips_enabled(3) and
    EVP_default_properties_enable_fips(3).

   Key generation is slower
    The Miller-Rabin test now uses 64 rounds, which is used for all prime
    generation, including RSA key generation. This affects the time for
    larger keys sizes.

    The default key generation method for the regular 2-prime RSA keys was
    changed to the FIPS186-4 B.3.6 method (Generation of Probable Primes
    with Conditions Based on Auxiliary Probable Primes). This method is
    slower than the original method.

   Change PBKDF2 to conform to SP800-132 instead of the older PKCS5 RFC2898
    This checks that the salt length is at least 128 bits, the derived key
    length is at least 112 bits, and that the iteration count is at least
    1000. For backwards compatibility these checks are disabled by default
    in the default provider, but are enabled by default in the FIPS
    provider.

    To enable or disable the checks see OSSL_KDF_PARAM_PKCS5 in
    EVP_KDF-PBKDF2(7). The parameter can be set using EVP_KDF_derive(3).

   Enforce a minimum DH modulus size of 512 bits
    Smaller sizes now result in an error.

   SM2 key changes
    EC EVP_PKEYs with the SM2 curve have been reworked to automatically
    become EVP_PKEY_SM2 rather than EVP_PKEY_EC.

    Unlike in previous OpenSSL versions, this means that applications cannot
    call EVP_PKEY_set_alias_type(pkey, EVP_PKEY_SM2) to get SM2
    computations.

    Parameter and key generation is also reworked to make it possible to
    generate EVP_PKEY_SM2 parameters and keys. Applications must now
    generate SM2 keys directly and must not create an EVP_PKEY_EC key first.
    It is no longer possible to import an SM2 key with domain parameters
    other than the SM2 elliptic curve ones.

    Validation of SM2 keys has been separated from the validation of regular
    EC keys, allowing to improve the SM2 validation process to reject loaded
    private keys that are not conforming to the SM2 ISO standard. In
    particular, a private scalar *k* outside the range *1 <= k < n-1* is now
    correctly rejected.

   EVP_PKEY_set_alias_type() method has been removed
    This function made a EVP_PKEY object mutable after it had been set up.
    In OpenSSL 3.0 it was decided that a provided key should not be able to
    change its type, so this function has been removed.

   Functions that return an internal key should be treated as read only
    Functions such as EVP_PKEY_get0_RSA(3) behave slightly differently in
    OpenSSL 3.0. Previously they returned a pointer to the low-level key
    used internally by libcrypto. From OpenSSL 3.0 this key may now be held
    in a provider. Calling these functions will only return a handle on the
    internal key where the EVP_PKEY was constructed using this key in the
    first place, for example using a function or macro such as
    EVP_PKEY_assign_RSA(3), EVP_PKEY_set1_RSA(3), etc. Where the EVP_PKEY
    holds a provider managed key, then these functions now return a cached
    copy of the key. Changes to the internal provider key that take place
    after the first time the cached key is accessed will not be reflected
    back in the cached copy. Similarly any changes made to the cached copy
    by application code will not be reflected back in the internal provider
    key.

    For the above reasons the keys returned from these functions should
    typically be treated as read-only. To emphasise this the value returned
    from EVP_PKEY_get0_RSA(3), EVP_PKEY_get0_DSA(3), EVP_PKEY_get0_EC_KEY(3)
    and EVP_PKEY_get0_DH(3) have been made const. This may break some
    existing code. Applications broken by this change should be modified.
    The preferred solution is to refactor the code to avoid the use of these
    deprecated functions. Failing this the code should be modified to use a
    const pointer instead. The EVP_PKEY_get1_RSA(3), EVP_PKEY_get1_DSA(3),
    EVP_PKEY_get1_EC_KEY(3) and EVP_PKEY_get1_DH(3) functions continue to
    return a non-const pointer to enable them to be "freed". However they
    should also be treated as read-only.

   The public key check has moved from EVP_PKEY_derive() to EVP_PKEY_derive_set_peer()
    This may mean result in an error in EVP_PKEY_derive_set_peer(3) rather
    than during EVP_PKEY_derive(3). To disable this check use
    EVP_PKEY_derive_set_peer_ex(dh, peer, 0).

   The print format has cosmetic changes for some functions
    The output from numerous "printing" functions such as
    X509_signature_print(3), X509_print_ex(3), X509_CRL_print_ex(3), and
    other similar functions has been amended such that there may be cosmetic
    differences between the output observed in 1.1.1 and 3.0. This also
    applies to the -text output from the openssl x509 and openssl crl
    applications.

   Interactive mode from the openssl program has been removed
    From now on, running it without arguments is equivalent to openssl help.

   The error return values from some control calls (ctrl) have changed
    One significant change is that controls which used to return -2 for
    invalid inputs, now return -1 indicating a generic error condition
    instead.

   DH and DHX key types have different settable parameters
    Previously (in 1.1.1) these conflicting parameters were allowed, but
    will now result in errors. See EVP_PKEY-DH(7) for further details. This
    affects the behaviour of openssl-genpkey(1) for DH parameter generation.

   EVP_CIPHER_CTX_set_flags() ordering change
    If using a cipher from a provider the EVP_CIPH_FLAG_LENGTH_BITS flag can
    only be set after the cipher has been assigned to the cipher context.
    See "FLAGS" in EVP_EncryptInit(3) for more information.

   Validation of operation context parameters
    Due to move of the implementation of cryptographic operations to the
    providers, validation of various operation parameters can be postponed
    until the actual operation is executed where previously it happened
    immediately when an operation parameter was set.

    For example when setting an unsupported curve with
    EVP_PKEY_CTX_set_ec_paramgen_curve_nid() this function call will not
    fail but later keygen operations with the EVP_PKEY_CTX will fail.

   Removal of function code from the error codes
    The function code part of the error code is now always set to 0. For
    that reason the ERR_GET_FUNC() macro was removed. Applications must
    resolve the error codes only using the library number and the reason
    code.

   ChaCha20-Poly1305 cipher does not allow a truncated IV length to be used
    In OpenSSL 3.0 setting the IV length to any value other than 12 will
    result in an error. Prior to OpenSSL 3.0 the ivlen could be smaller that
    the required 12 byte length, using EVP_CIPHER_CTX_ctrl(ctx,
    EVP_CRTL_AEAD_SET_IVLEN, ivlen, NULL). This resulted in an IV that had
    leading zero padding.

  Installation and Compilation
    Please refer to the INSTALL.md file in the top of the distribution for
    instructions on how to build and install OpenSSL 3.0. Please also refer
    to the various platform specific NOTES files for your specific platform.

  Upgrading from OpenSSL 1.1.1
    Upgrading to OpenSSL 3.0 from OpenSSL 1.1.1 should be relatively
    straight forward in most cases. The most likely area where you will
    encounter problems is if you have used low level APIs in your code (as
    discussed above). In that case you are likely to start seeing
    deprecation warnings when compiling your application. If this happens
    you have 3 options:

    1.  Ignore the warnings. They are just warnings. The deprecated
        functions are still present and you may still use them. However be
        aware that they may be removed from a future version of OpenSSL.

    2.  Suppress the warnings. Refer to your compiler documentation on how
        to do this.

    3.  Remove your usage of the low level APIs. In this case you will need
        to rewrite your code to use the high level APIs instead

   Error code changes
    As OpenSSL 3.0 provides a brand new Encoder/Decoder mechanism for
    working with widely used file formats, application code that checks for
    particular error reason codes on key loading failures might need an
    update.

    Password-protected keys may deserve special attention. If only some
    errors are treated as an indicator that the user should be asked about
    the password again, it's worth testing these scenarios and processing
    the newly relevant codes.

    There may be more cases to treat specially, depending on the calling
    application code.

  Upgrading from OpenSSL 1.0.2
    Upgrading to OpenSSL 3.0 from OpenSSL 1.0.2 is likely to be
    significantly more difficult. In addition to the issues discussed above
    in the section about "Upgrading from OpenSSL 1.1.1", the main things to
    be aware of are:

    1.  The build and installation procedure has changed significantly.

        Check the file INSTALL.md in the top of the installation for
        instructions on how to build and install OpenSSL for your platform.
        Also read the various NOTES files in the same directory, as
        applicable for your platform.

    2.  Many structures have been made opaque in OpenSSL 3.0.

        The structure definitions have been removed from the public header
        files and moved to internal header files. In practice this means
        that you can no longer stack allocate some structures. Instead they
        must be heap allocated through some function call (typically those
        function names have a "_new" suffix to them). Additionally you must
        use "setter" or "getter" functions to access the fields within those
        structures.

        For example code that previously looked like this:

         EVP_MD_CTX md_ctx;

         /* This line will now generate compiler errors */
         EVP_MD_CTX_init(&md_ctx);

        The code needs to be amended to look like this:

         EVP_MD_CTX *md_ctx;

         md_ctx = EVP_MD_CTX_new();
         ...
         ...
         EVP_MD_CTX_free(md_ctx);

    3.  Support for TLSv1.3 has been added.

        This has a number of implications for SSL/TLS applications. See the
        TLS1.3 page <https://github.com/openssl/openssl/wiki/TLS1.3> for
        further details.

    More details about the breaking changes between OpenSSL versions 1.0.2
    and 1.1.0 can be found on the OpenSSL 1.1.0 Changes page
    <https://github.com/openssl/openssl/wiki/OpenSSL_1.1.0_Changes>.

   Upgrading from the OpenSSL 2.0 FIPS Object Module
    The OpenSSL 2.0 FIPS Object Module was a separate download that had to
    be built separately and then integrated into your main OpenSSL 1.0.2
    build. In OpenSSL 3.0 the FIPS support is fully integrated into the
    mainline version of OpenSSL and is no longer a separate download. For
    further information see "Completing the installation of the FIPS
    Module".

    The function calls FIPS_mode() and FIPS_mode_set() have been removed
    from OpenSSL 3.0. You should rewrite your application to not use them.
    See fips_module(7) and OSSL_PROVIDER-FIPS(7) for details.

  Completing the installation of the FIPS Module
    The FIPS Module will be built and installed automatically if FIPS
    support has been configured. The current documentation can be found in
    the README-FIPS
    <https://github.com/openssl/openssl/blob/master/README-FIPS.md> file.

  Programming
    Applications written to work with OpenSSL 1.1.1 will mostly just work
    with OpenSSL 3.0. However changes will be required if you want to take
    advantage of some of the new features that OpenSSL 3.0 makes available.
    In order to do that you need to understand some new concepts introduced
    in OpenSSL 3.0. Read "Library contexts" in crypto(7) for further
    information.

   Library Context
    A library context allows different components of a complex application
    to each use a different library context and have different providers
    loaded with different configuration settings. See "Library contexts" in
    crypto(7) for further info.

    If the user creates an OSSL_LIB_CTX via OSSL_LIB_CTX_new(3) then many
    functions may need to be changed to pass additional parameters to handle
    the library context.

   Using a Library Context - Old functions that should be changed
    If a library context is needed then all EVP_* digest functions that
    return a const EVP_MD * such as EVP_sha256() should be replaced with a
    call to EVP_MD_fetch(3). See "ALGORITHM FETCHING" in crypto(7).

    If a library context is needed then all EVP_* cipher functions that
    return a const EVP_CIPHER * such as EVP_aes_128_cbc() should be replaced
    vith a call to EVP_CIPHER_fetch(3). See "ALGORITHM FETCHING" in
    crypto(7).

    Some functions can be passed an object that has already been set up with
    a library context such as d2i_X509(3), d2i_X509_CRL(3), d2i_X509_REQ(3)
    and d2i_X509_PUBKEY(3). If NULL is passed instead then the created
    object will be set up with the default library context. Use
    X509_new_ex(3), X509_CRL_new_ex(3), X509_REQ_new_ex(3) and
    X509_PUBKEY_new_ex(3) if a library context is required.

    All functions listed below with a *NAME* have a replacement function
    *NAME_ex* that takes OSSL_LIB_CTX as an additional argument. Functions
    that have other mappings are listed along with the respective name.

    *   ASN1_item_new(3), ASN1_item_d2i(3), ASN1_item_d2i_fp(3),
        ASN1_item_d2i_bio(3), ASN1_item_sign(3) and ASN1_item_verify(3)

    *   BIO_new(3)

    *   b2i_RSA_PVK_bio() and i2b_PVK_bio()

    *   BN_CTX_new(3) and BN_CTX_secure_new(3)

    *   CMS_AuthEnvelopedData_create(3), CMS_ContentInfo_new(3),
        CMS_data_create(3), CMS_digest_create(3),
        CMS_EncryptedData_encrypt(3), CMS_encrypt(3),
        CMS_EnvelopedData_create(3), CMS_ReceiptRequest_create0(3) and
        CMS_sign(3)

    *   CONF_modules_load_file(3)

    *   CTLOG_new(3), CTLOG_new_from_base64(3) and CTLOG_STORE_new(3)

    *   CT_POLICY_EVAL_CTX_new(3)

    *   d2i_AutoPrivateKey(3), d2i_PrivateKey(3) and d2i_PUBKEY(3)

    *   d2i_PrivateKey_bio(3) and d2i_PrivateKey_fp(3)

        Use d2i_PrivateKey_ex_bio(3) and d2i_PrivateKey_ex_fp(3)

    *   EC_GROUP_new(3)

        Use EC_GROUP_new_by_curve_name_ex(3) or EC_GROUP_new_from_params(3).

    *   EVP_DigestSignInit(3) and EVP_DigestVerifyInit(3)

    *   EVP_PBE_CipherInit(3), EVP_PBE_find(3) and EVP_PBE_scrypt(3)

    *   PKCS5_PBE_keyivgen(3)

    *   EVP_PKCS82PKEY(3)

    *   EVP_PKEY_CTX_new_id(3)

        Use EVP_PKEY_CTX_new_from_name(3)

    *   EVP_PKEY_derive_set_peer(3), EVP_PKEY_new_raw_private_key(3) and
        EVP_PKEY_new_raw_public_key(3)

    *   EVP_SignFinal(3) and EVP_VerifyFinal(3)

    *   NCONF_new(3)

    *   OCSP_RESPID_match(3) and OCSP_RESPID_set_by_key(3)

    *   OPENSSL_thread_stop(3)

    *   OSSL_STORE_open(3)

    *   PEM_read_bio_Parameters(3), PEM_read_bio_PrivateKey(3),
        PEM_read_bio_PUBKEY(3), PEM_read_PrivateKey(3) and
        PEM_read_PUBKEY(3)

    *   PEM_write_bio_PrivateKey(3), PEM_write_bio_PUBKEY(3),
        PEM_write_PrivateKey(3) and PEM_write_PUBKEY(3)

    *   PEM_X509_INFO_read_bio(3) and PEM_X509_INFO_read(3)

    *   PKCS12_add_key(3), PKCS12_add_safe(3), PKCS12_add_safes(3),
        PKCS12_create(3), PKCS12_decrypt_skey(3), PKCS12_init(3),
        PKCS12_item_decrypt_d2i(3), PKCS12_item_i2d_encrypt(3),
        PKCS12_key_gen_asc(3), PKCS12_key_gen_uni(3),
        PKCS12_key_gen_utf8(3), PKCS12_pack_p7encdata(3),
        PKCS12_pbe_crypt(3), PKCS12_PBE_keyivgen(3),
        PKCS12_SAFEBAG_create_pkcs8_encrypt(3)

    *   PKCS5_pbe_set0_algor(3), PKCS5_pbe_set(3), PKCS5_pbe2_set_iv(3),
        PKCS5_pbkdf2_set(3) and PKCS5_v2_scrypt_keyivgen(3)

    *   PKCS7_encrypt(3), PKCS7_new(3) and PKCS7_sign(3)

    *   PKCS8_decrypt(3), PKCS8_encrypt(3) and PKCS8_set0_pbe(3)

    *   RAND_bytes(3) and RAND_priv_bytes(3)

    *   SMIME_write_ASN1(3)

    *   SSL_load_client_CA_file(3)

    *   SSL_CTX_new(3)

    *   TS_RESP_CTX_new(3)

    *   X509_CRL_new(3)

    *   X509_load_cert_crl_file(3) and X509_load_cert_file(3)

    *   X509_LOOKUP_by_subject(3) and X509_LOOKUP_ctrl(3)

    *   X509_NAME_hash(3)

    *   X509_new(3)

    *   X509_REQ_new(3) and X509_REQ_verify(3)

    *   X509_STORE_CTX_new(3), X509_STORE_set_default_paths(3),
        X509_STORE_load_file(3), X509_STORE_load_locations(3) and
        X509_STORE_load_store(3)

   New functions that use a Library context
    The following functions can be passed a library context if required.
    Passing NULL will use the default library context.

    *   BIO_new_from_core_bio(3)

    *   EVP_ASYM_CIPHER_fetch(3) and EVP_ASYM_CIPHER_do_all_provided(3)

    *   EVP_CIPHER_fetch(3) and EVP_CIPHER_do_all_provided(3)

    *   EVP_default_properties_enable_fips(3) and
        EVP_default_properties_is_fips_enabled(3)

    *   EVP_KDF_fetch(3) and EVP_KDF_do_all_provided(3)

    *   EVP_KEM_fetch(3) and EVP_KEM_do_all_provided(3)

    *   EVP_KEYEXCH_fetch(3) and EVP_KEYEXCH_do_all_provided(3)

    *   EVP_KEYMGMT_fetch(3) and EVP_KEYMGMT_do_all_provided(3)

    *   EVP_MAC_fetch(3) and EVP_MAC_do_all_provided(3)

    *   EVP_MD_fetch(3) and EVP_MD_do_all_provided(3)

    *   EVP_PKEY_CTX_new_from_pkey(3)

    *   EVP_PKEY_Q_keygen(3)

    *   EVP_Q_mac(3) and EVP_Q_digest(3)

    *   EVP_RAND(3) and EVP_RAND_do_all_provided(3)

    *   EVP_set_default_properties(3)

    *   EVP_SIGNATURE_fetch(3) and EVP_SIGNATURE_do_all_provided(3)

    *   OSSL_CMP_CTX_new(3) and OSSL_CMP_SRV_CTX_new(3)

    *   OSSL_CRMF_ENCRYPTEDVALUE_get1_encCert(3)

    *   OSSL_CRMF_MSG_create_popo(3) and OSSL_CRMF_MSGS_verify_popo(3)

    *   OSSL_CRMF_pbm_new(3) and OSSL_CRMF_pbmp_new(3)

    *   OSSL_DECODER_CTX_add_extra(3) and OSSL_DECODER_CTX_new_for_pkey(3)

    *   OSSL_DECODER_fetch(3) and OSSL_DECODER_do_all_provided(3)

    *   OSSL_ENCODER_CTX_add_extra(3)

    *   OSSL_ENCODER_fetch(3) and OSSL_ENCODER_do_all_provided(3)

    *   OSSL_LIB_CTX_free(3), OSSL_LIB_CTX_load_config(3) and
        OSSL_LIB_CTX_set0_default(3)

    *   OSSL_PROVIDER_add_builtin(3), OSSL_PROVIDER_available(3),
        OSSL_PROVIDER_do_all(3), OSSL_PROVIDER_load(3),
        OSSL_PROVIDER_set_default_search_path(3) and
        OSSL_PROVIDER_try_load(3)

    *   OSSL_SELF_TEST_get_callback(3) and OSSL_SELF_TEST_set_callback(3)

    *   OSSL_STORE_attach(3)

    *   OSSL_STORE_LOADER_fetch(3) and OSSL_STORE_LOADER_do_all_provided(3)

    *   RAND_get0_primary(3), RAND_get0_private(3), RAND_get0_public(3),
        RAND_set_DRBG_type(3) and RAND_set_seed_source_type(3)

   Providers
    Providers are described in detail here "Providers" in crypto(7). See
    also "OPENSSL PROVIDERS" in crypto(7).

   Fetching algorithms and property queries
    Implicit and Explicit Fetching is described in detail here "ALGORITHM
    FETCHING" in crypto(7).

   Mapping EVP controls and flags to provider OSSL_PARAM(3) parameters
    The existing functions for controls (such as EVP_CIPHER_CTX_ctrl(3)) and
    manipulating flags (such as EVP_MD_CTX_set_flags(3))internally use
    OSSL_PARAMS to pass information to/from provider objects. See
    OSSL_PARAM(3) for additional information related to parameters.

    For ciphers see "CONTROLS" in EVP_EncryptInit(3), "FLAGS" in
    EVP_EncryptInit(3) and "PARAMETERS" in EVP_EncryptInit(3).

    For digests see "CONTROLS" in EVP_DigestInit(3), "FLAGS" in
    EVP_DigestInit(3) and "PARAMETERS" in EVP_DigestInit(3).

   Deprecation of Low Level Functions
    A significant number of APIs have been deprecated in OpenSSL 3.0. This
    section describes some common categories of deprecations. See
    "Deprecated function mappings" for the list of deprecated functions that
    refer to these categories.

   Providers are a replacement for engines and low-level method overrides
    Any accessor that uses an ENGINE is deprecated (such as
    EVP_PKEY_set1_engine()). Applications using engines should instead use
    providers.

    Before providers were added algorithms were overridden by changing the
    methods used by algorithms. All these methods such as RSA_new_method()
    and RSA_meth_new() are now deprecated and can be replaced by using
    providers instead.

   Deprecated i2d and d2i functions for low-level key types
    Any i2d and d2i functions such as d2i_DHparams() that take a low-level
    key type have been deprecated. Applications should instead use the
    OSSL_DECODER(3) and OSSL_ENCODER(3) APIs to read and write files. See
    "Migration" in d2i_RSAPrivateKey(3) for further details.

   Deprecated low-level key object getters and setters
    Applications that set or get low-level key objects (such as
    EVP_PKEY_set1_DH() or EVP_PKEY_get0()) should instead use the
    OSSL_ENCODER (See OSSL_ENCODER_to_bio(3)) or OSSL_DECODER (See
    OSSL_DECODER_from_bio(3)) APIs, or alternatively use
    EVP_PKEY_fromdata(3) or EVP_PKEY_todata(3).

   Deprecated low-level key parameter getters
    Functions that access low-level objects directly such as RSA_get0_n(3)
    are now deprecated. Applications should use one of:
    EVP_PKEY_get_bn_param(3), EVP_PKEY_get_int_param(3),
    EVP_PKEY_get_size_t_param(3), EVP_PKEY_get_utf8_string_param(3),
    EVP_PKEY_get_octet_string_param(3), or EVP_PKEY_get_params(3), to access
    fields from an EVP_PKEY. Gettable parameters are listed in: "Common RSA
    parameters" in EVP_PKEY-RSA(7), "Common EC parameters" in
    EVP_PKEY-EC(7), "DSA parameters" in EVP_PKEY-DSA(7), "DH parameters" in
    EVP_PKEY-DH(7), "FFC parameters" in EVP_PKEY-FFC(7), "Common X25519,
    X448, ED25519 and ED448 parameters" in EVP_PKEY-X25519(7), "Common
    parameters" in EVP_PKEY-ML-DSA(7), and "Common parameters" in
    EVP_PKEY-ML-KEM(7). Applications may also use EVP_PKEY_todata(3) to
    return all fields.

   Deprecated low-level key parameter setters
    Functions that access low-level objects directly such as
    RSA_set0_crt_params(3) are now deprecated. Applications should use
    EVP_PKEY_fromdata(3) to create new keys from user provided key data.
    Keys should be immutable once they are created, so if required the user
    may use EVP_PKEY_todata(3), OSSL_PARAM_merge(3), and
    EVP_PKEY_fromdata(3) to create a modified key. See "Examples" in
    EVP_PKEY-DH(7) for more information. See "Deprecated low-level key
    generation functions" for information on generating a key using
    parameters.

   Deprecated low-level object creation
    Low-level objects were created using methods such as RSA_new(3),
    RSA_up_ref(3) and RSA_free(3). Applications should instead use the
    high-level EVP_PKEY APIs, e.g. EVP_PKEY_new(3), EVP_PKEY_up_ref(3) and
    EVP_PKEY_free(3). See also EVP_PKEY_CTX_new_from_name(3) and
    EVP_PKEY_CTX_new_from_pkey(3).

    EVP_PKEYs may be created in a variety of ways: See also "Deprecated
    low-level key generation functions", "Deprecated low-level key reading
    and writing functions" and "Deprecated low-level key parameter setters".

   Deprecated low-level encryption functions
    Low-level encryption functions such as AES_encrypt(3) and AES_decrypt(3)
    have been informally discouraged from use for a long time. Applications
    should instead use the high level EVP APIs EVP_EncryptInit_ex(3),
    EVP_EncryptUpdate(3), and EVP_EncryptFinal_ex(3) or
    EVP_DecryptInit_ex(3), EVP_DecryptUpdate(3) and EVP_DecryptFinal_ex(3).

   Deprecated low-level digest functions
    Use of low-level digest functions such as SHA1_Init(3) have been
    informally discouraged from use for a long time. Applications should
    instead use the high level EVP APIs EVP_DigestInit_ex(3),
    EVP_DigestUpdate(3) and EVP_DigestFinal_ex(3), or the quick one-shot
    EVP_Q_digest(3).

    Note that the functions SHA1(3), SHA224(3), SHA256(3), SHA384(3) and
    SHA512(3) have changed to macros that use EVP_Q_digest(3).

   Deprecated low-level signing functions
    Use of low-level signing functions such as DSA_sign(3) have been
    informally discouraged for a long time. Instead applications should use
    EVP_DigestSign(3) and EVP_DigestVerify(3). See also
    EVP_SIGNATURE-RSA(7), EVP_SIGNATURE-DSA(7), EVP_SIGNATURE-ECDSA(7) and
    EVP_SIGNATURE-ED25519(7).

   Deprecated low-level MAC functions
    Low-level mac functions such as CMAC_Init(3) are deprecated.
    Applications should instead use the new EVP_MAC(3) interface, using
    EVP_MAC_CTX_new(3), EVP_MAC_CTX_free(3), EVP_MAC_init(3),
    EVP_MAC_update(3) and EVP_MAC_final(3) or the single-shot MAC function
    EVP_Q_mac(3). See EVP_MAC(3), EVP_MAC-HMAC(7), EVP_MAC-CMAC(7),
    EVP_MAC-GMAC(7), EVP_MAC-KMAC(7), EVP_MAC-BLAKE2(7), EVP_MAC-Poly1305(7)
    and EVP_MAC-Siphash(7) for additional information.

    Note that the one-shot method HMAC() is still available for
    compatibility purposes, but this can also be replaced by using EVP_Q_MAC
    if a library context is required.

   Deprecated low-level validation functions
    Low-level validation functions such as DH_check(3) have been informally
    discouraged from use for a long time. Applications should instead use
    the high-level EVP_PKEY APIs such as EVP_PKEY_check(3),
    EVP_PKEY_param_check(3), EVP_PKEY_param_check_quick(3),
    EVP_PKEY_public_check(3), EVP_PKEY_public_check_quick(3),
    EVP_PKEY_private_check(3), and EVP_PKEY_pairwise_check(3).

   Deprecated low-level key exchange functions
    Many low-level functions have been informally discouraged from use for a
    long time. Applications should instead use EVP_PKEY_derive(3). See
    EVP_KEYEXCH-DH(7), EVP_KEYEXCH-ECDH(7) and EVP_KEYEXCH-X25519(7).

   Deprecated low-level key generation functions
    Many low-level functions have been informally discouraged from use for a
    long time. Applications should instead use EVP_PKEY_keygen_init(3) and
    EVP_PKEY_generate(3) as described in EVP_PKEY-DSA(7), EVP_PKEY-DH(7),
    EVP_PKEY-RSA(7), EVP_PKEY-EC(7) and EVP_PKEY-X25519(7). The 'quick'
    one-shot function EVP_PKEY_Q_keygen(3) and macros for the most common
    cases: <EVP_RSA_gen(3)> and EVP_EC_gen(3) may also be used.

   Deprecated low-level key reading and writing functions
    Use of low-level objects (such as DSA) has been informally discouraged
    from use for a long time. Functions to read and write these low-level
    objects (such as PEM_read_DSA_PUBKEY()) should be replaced. Applications
    should instead use OSSL_ENCODER_to_bio(3) and OSSL_DECODER_from_bio(3).

   Deprecated low-level key printing functions
    Use of low-level objects (such as DSA) has been informally discouraged
    from use for a long time. Functions to print these low-level objects
    such as DSA_print() should be replaced with the equivalent EVP_PKEY
    functions. Application should use one of EVP_PKEY_print_public(3),
    EVP_PKEY_print_private(3), EVP_PKEY_print_params(3),
    EVP_PKEY_print_public_fp(3), EVP_PKEY_print_private_fp(3) or
    EVP_PKEY_print_params_fp(3). Note that internally these use
    OSSL_ENCODER_to_bio(3) and OSSL_DECODER_from_bio(3).

   Deprecated function mappings
    The following functions have been deprecated in 3.0.

    *   AES_bi_ige_encrypt() and AES_ige_encrypt()

        There is no replacement for the IGE functions. New code should not
        use these modes. These undocumented functions were never integrated
        into the EVP layer. They implemented the AES Infinite Garble
        Extension (IGE) mode and AES Bi-directional IGE mode. These modes
        were never formally standardised and usage of these functions is
        believed to be very small. In particular AES_bi_ige_encrypt() has a
        known bug. It accepts 2 AES keys, but only one is ever used. The
        security implications are believed to be minimal, but this issue was
        never fixed for backwards compatibility reasons.

    *   AES_encrypt(), AES_decrypt(), AES_set_encrypt_key(),
        AES_set_decrypt_key(), AES_cbc_encrypt(), AES_cfb128_encrypt(),
        AES_cfb1_encrypt(), AES_cfb8_encrypt(), AES_ecb_encrypt(),
        AES_ofb128_encrypt()

    *   AES_unwrap_key(), AES_wrap_key()

        See "Deprecated low-level encryption functions"

    *   AES_options()

        There is no replacement. It returned a string indicating if the AES
        code was unrolled.

    *   ASN1_digest(), ASN1_sign(), ASN1_verify()

        There are no replacements. These old functions are not used, and
        could be disabled with the macro NO_ASN1_OLD since OpenSSL 0.9.7.

    *   ASN1_STRING_length_set()

        Use ASN1_STRING_set(3) or ASN1_STRING_set0(3) instead. This was a
        potentially unsafe function that could change the bounds of a
        previously passed in pointer.

    *   BF_encrypt(), BF_decrypt(), BF_set_key(), BF_cbc_encrypt(),
        BF_cfb64_encrypt(), BF_ecb_encrypt(), BF_ofb64_encrypt()

        See "Deprecated low-level encryption functions". The Blowfish
        algorithm has been moved to the Legacy Provider.

    *   BF_options()

        There is no replacement. This option returned a constant string.

    *   BIO_get_callback(), BIO_set_callback(), BIO_debug_callback()

        Use the respective non-deprecated _ex() functions.

    *   BN_is_prime_ex(), BN_is_prime_fasttest_ex()

        Use BN_check_prime(3) which avoids possible misuse and always uses
        at least 64 rounds of the Miller-Rabin primality test.

    *   BN_pseudo_rand(), BN_pseudo_rand_range()

        Use BN_rand(3) and BN_rand_range(3).

    *   BN_X931_derive_prime_ex(), BN_X931_generate_prime_ex(),
        BN_X931_generate_Xpq()

        There are no replacements for these low-level functions. They were
        used internally by RSA_X931_derive_ex() and
        RSA_X931_generate_key_ex() which are also deprecated. Use
        EVP_PKEY_keygen(3) instead.

    *   Camellia_encrypt(), Camellia_decrypt(), Camellia_set_key(),
        Camellia_cbc_encrypt(), Camellia_cfb128_encrypt(),
        Camellia_cfb1_encrypt(), Camellia_cfb8_encrypt(),
        Camellia_ctr128_encrypt(), Camellia_ecb_encrypt(),
        Camellia_ofb128_encrypt()

        See "Deprecated low-level encryption functions".

    *   CAST_encrypt(), CAST_decrypt(), CAST_set_key(), CAST_cbc_encrypt(),
        CAST_cfb64_encrypt(), CAST_ecb_encrypt(), CAST_ofb64_encrypt()

        See "Deprecated low-level encryption functions". The CAST algorithm
        has been moved to the Legacy Provider.

    *   CMAC_CTX_new(), CMAC_CTX_cleanup(), CMAC_CTX_copy(),
        CMAC_CTX_free(), CMAC_CTX_get0_cipher_ctx()

        See "Deprecated low-level MAC functions".

    *   CMAC_Init(), CMAC_Update(), CMAC_Final(), CMAC_resume()

        See "Deprecated low-level MAC functions".

    *   CRYPTO_mem_ctrl(), CRYPTO_mem_debug_free(),
        CRYPTO_mem_debug_malloc(), CRYPTO_mem_debug_pop(),
        CRYPTO_mem_debug_push(), CRYPTO_mem_debug_realloc(),
        CRYPTO_mem_leaks(), CRYPTO_mem_leaks_cb(), CRYPTO_mem_leaks_fp(),
        CRYPTO_set_mem_debug()

        Memory-leak checking has been deprecated in favor of more modern
        development tools, such as compiler memory and leak sanitizers or
        Valgrind.

    *   CRYPTO_cts128_encrypt_block(), CRYPTO_cts128_encrypt(),
        CRYPTO_cts128_decrypt_block(), CRYPTO_cts128_decrypt(),
        CRYPTO_nistcts128_encrypt_block(), CRYPTO_nistcts128_encrypt(),
        CRYPTO_nistcts128_decrypt_block(), CRYPTO_nistcts128_decrypt()

        Use the higher level functions EVP_CipherInit_ex2(),
        EVP_CipherUpdate() and EVP_CipherFinal_ex() instead. See the
        "cts_mode" parameter in "Gettable and Settable EVP_CIPHER_CTX
        parameters" in EVP_EncryptInit(3). See "EXAMPLES" in
        EVP_EncryptInit(3) for a AES-256-CBC-CTS example.

    *   d2i_DHparams(), d2i_DHxparams(), d2i_DSAparams(),
        d2i_DSAPrivateKey(), d2i_DSAPrivateKey_bio(),
        d2i_DSAPrivateKey_fp(), d2i_DSA_PUBKEY(), d2i_DSA_PUBKEY_bio(),
        d2i_DSA_PUBKEY_fp(), d2i_DSAPublicKey(), d2i_ECParameters(),
        d2i_ECPrivateKey(), d2i_ECPrivateKey_bio(), d2i_ECPrivateKey_fp(),
        d2i_EC_PUBKEY(), d2i_EC_PUBKEY_bio(), d2i_EC_PUBKEY_fp(),
        d2i_RSAPrivateKey(), d2i_RSAPrivateKey_bio(),
        d2i_RSAPrivateKey_fp(), d2i_RSA_PUBKEY(), d2i_RSA_PUBKEY_bio(),
        d2i_RSA_PUBKEY_fp(), d2i_RSAPublicKey(), d2i_RSAPublicKey_bio(),
        d2i_RSAPublicKey_fp()

        See "Deprecated i2d and d2i functions for low-level key types"

    *   o2i_ECPublicKey()

        Use EVP_PKEY_set1_encoded_public_key(3). See "Deprecated low-level
        key parameter setters"

    *   DES_crypt(), DES_fcrypt(), DES_encrypt1(), DES_encrypt2(),
        DES_encrypt3(), DES_decrypt3(), DES_ede3_cbc_encrypt(),
        DES_ede3_cfb64_encrypt(),
        DES_ede3_cfb_encrypt(),DES_ede3_ofb64_encrypt(), DES_ecb_encrypt(),
        DES_ecb3_encrypt(), DES_ofb64_encrypt(), DES_ofb_encrypt(),
        DES_cfb64_encrypt DES_cfb_encrypt(), DES_cbc_encrypt(),
        DES_ncbc_encrypt(), DES_pcbc_encrypt(), DES_xcbc_encrypt(),
        DES_cbc_cksum(), DES_quad_cksum(), DES_check_key_parity(),
        DES_is_weak_key(), DES_key_sched(), DES_options(), DES_random_key(),
        DES_set_key(), DES_set_key_checked(), DES_set_key_unchecked(),
        DES_set_odd_parity(), DES_string_to_2keys(), DES_string_to_key()

        See "Deprecated low-level encryption functions". Algorithms for
        "DESX-CBC", "DES-ECB", "DES-CBC", "DES-OFB", "DES-CFB", "DES-CFB1"
        and "DES-CFB8" have been moved to the Legacy Provider.

    *   DH_bits(), DH_security_bits(), DH_size()

        Use EVP_PKEY_get_bits(3), EVP_PKEY_get_security_bits(3) and
        EVP_PKEY_get_size(3).

    *   DH_check(), DH_check_ex(), DH_check_params(), DH_check_params_ex(),
        DH_check_pub_key(), DH_check_pub_key_ex()

        See "Deprecated low-level validation functions"

    *   DH_clear_flags(), DH_test_flags(), DH_set_flags()

        The DH_FLAG_CACHE_MONT_P flag has been deprecated without
        replacement. The DH_FLAG_TYPE_DH and DH_FLAG_TYPE_DHX have been
        deprecated. Use EVP_PKEY_is_a() to determine the type of a key.
        There is no replacement for setting these flags.

    *   DH_compute_key() DH_compute_key_padded()

        See "Deprecated low-level key exchange functions".

    *   DH_new(), DH_new_by_nid(), DH_free(), DH_up_ref()

        See "Deprecated low-level object creation"

    *   DH_generate_key(), DH_generate_parameters_ex()

        See "Deprecated low-level key generation functions".

    *   DH_get0_pqg(), DH_get0_p(), DH_get0_q(), DH_get0_g(), DH_get0_key(),
        DH_get0_priv_key(), DH_get0_pub_key(), DH_get_length(), DH_get_nid()

        See "Deprecated low-level key parameter getters"

    *   DH_get_1024_160(), DH_get_2048_224(), DH_get_2048_256()

        Applications should instead set the OSSL_PKEY_PARAM_GROUP_NAME as
        specified in "DH parameters" in EVP_PKEY-DH(7)) to one of
        "dh_1024_160", "dh_2048_224" or "dh_2048_256" when generating a DH
        key.

    *   DH_KDF_X9_42()

        Applications should use EVP_PKEY_CTX_set_dh_kdf_type(3) instead.

    *   DH_get_default_method(), DH_get0_engine(), DH_meth_*(),
        DH_new_method(), DH_OpenSSL(), DH_get_ex_data(),
        DH_set_default_method(), DH_set_method(), DH_set_ex_data()

        See "Providers are a replacement for engines and low-level method
        overrides"

    *   DHparams_print(), DHparams_print_fp()

        See "Deprecated low-level key printing functions"

    *   DH_set0_key(), DH_set0_pqg(), DH_set_length()

        See "Deprecated low-level key parameter setters"

    *   DSA_bits(), DSA_security_bits(), DSA_size()

        Use EVP_PKEY_get_bits(3), EVP_PKEY_get_security_bits(3) and
        EVP_PKEY_get_size(3).

    *   DHparams_dup(), DSA_dup_DH()

        There is no direct replacement. Applications may use
        EVP_PKEY_copy_parameters(3) and EVP_PKEY_dup(3) instead.

    *   DSA_generate_key(), DSA_generate_parameters_ex()

        See "Deprecated low-level key generation functions".

    *   DSA_get0_engine(), DSA_get_default_method(), DSA_get_ex_data(),
        DSA_get_method(), DSA_meth_*(), DSA_new_method(), DSA_OpenSSL(),
        DSA_set_default_method(), DSA_set_ex_data(), DSA_set_method()

        See "Providers are a replacement for engines and low-level method
        overrides".

    *   DSA_get0_p(), DSA_get0_q(), DSA_get0_g(), DSA_get0_pqg(),
        DSA_get0_key(), DSA_get0_priv_key(), DSA_get0_pub_key()

        See "Deprecated low-level key parameter getters".

    *   DSA_new(), DSA_free(), DSA_up_ref()

        See "Deprecated low-level object creation"

    *   DSAparams_dup()

        There is no direct replacement. Applications may use
        EVP_PKEY_copy_parameters(3) and EVP_PKEY_dup(3) instead.

    *   DSAparams_print(), DSAparams_print_fp(), DSA_print(), DSA_print_fp()

        See "Deprecated low-level key printing functions"

    *   DSA_set0_key(), DSA_set0_pqg()

        See "Deprecated low-level key parameter setters"

    *   DSA_set_flags(), DSA_clear_flags(), DSA_test_flags()

        The DSA_FLAG_CACHE_MONT_P flag has been deprecated without
        replacement.

    *   DSA_sign(), DSA_do_sign(), DSA_sign_setup(), DSA_verify(),
        DSA_do_verify()

        See "Deprecated low-level signing functions".

    *   ECDH_compute_key()

        See "Deprecated low-level key exchange functions".

    *   ECDH_KDF_X9_62()

        Applications may either set this using the helper function
        EVP_PKEY_CTX_set_ecdh_kdf_type(3) or by setting an OSSL_PARAM(3)
        using the "kdf-type" as shown in "EXAMPLES" in EVP_KEYEXCH-ECDH(7)

    *   ECDSA_sign(), ECDSA_sign_ex(), ECDSA_sign_setup(), ECDSA_do_sign(),
        ECDSA_do_sign_ex(), ECDSA_verify(), ECDSA_do_verify()

        See "Deprecated low-level signing functions".

    *   ECDSA_size()

        Applications should use EVP_PKEY_get_size(3).

    *   EC_GF2m_simple_method(), EC_GFp_mont_method(), EC_GFp_nist_method(),
        EC_GFp_nistp224_method(), EC_GFp_nistp256_method(),
        EC_GFp_nistp521_method(), EC_GFp_simple_method()

        There are no replacements for these functions. Applications should
        rely on the library automatically assigning a suitable method
        internally when an EC_GROUP is constructed.

    *   EC_GROUP_clear_free()

        Use EC_GROUP_free(3) instead.

    *   EC_GROUP_get_curve_GF2m(), EC_GROUP_get_curve_GFp(),
        EC_GROUP_set_curve_GF2m(), EC_GROUP_set_curve_GFp()

        Applications should use EC_GROUP_get_curve(3) and
        EC_GROUP_set_curve(3).

    *   EC_GROUP_have_precompute_mult(), EC_GROUP_precompute_mult(),
        EC_KEY_precompute_mult()

        These functions are not widely used. Applications should instead
        switch to named curves which OpenSSL has hardcoded lookup tables
        for.

    *   EC_GROUP_new(), EC_GROUP_method_of(), EC_POINT_method_of()

        EC_METHOD is now an internal-only concept and a suitable EC_METHOD
        is assigned internally without application intervention. Users of
        EC_GROUP_new() should switch to a different suitable constructor.

    *   EC_KEY_can_sign()

        Applications should use EVP_PKEY_can_sign(3) instead.

    *   EC_KEY_check_key()

        See "Deprecated low-level validation functions"

    *   EC_KEY_set_flags(), EC_KEY_get_flags(), EC_KEY_clear_flags()

        See "Common EC parameters" in EVP_PKEY-EC(7) which handles flags as
        separate parameters for OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMAT,
        OSSL_PKEY_PARAM_EC_GROUP_CHECK_TYPE, OSSL_PKEY_PARAM_EC_ENCODING,
        OSSL_PKEY_PARAM_USE_COFACTOR_ECDH and
        OSSL_PKEY_PARAM_EC_INCLUDE_PUBLIC. See also "EXAMPLES" in
        EVP_PKEY-EC(7)

    *   EC_KEY_dup(), EC_KEY_copy()

        There is no direct replacement. Applications may use
        EVP_PKEY_copy_parameters(3) and EVP_PKEY_dup(3) instead.

    *   EC_KEY_decoded_from_explicit_params()

        There is no replacement.

    *   EC_KEY_generate_key()

        See "Deprecated low-level key generation functions".

    *   EC_KEY_get0_group(), EC_KEY_get0_private_key(),
        EC_KEY_get0_public_key(), EC_KEY_get_conv_form(),
        EC_KEY_get_enc_flags()

        See "Deprecated low-level key parameter getters".

    *   EC_KEY_get0_engine(), EC_KEY_get_default_method(),
        EC_KEY_get_method(), EC_KEY_new_method(), EC_KEY_get_ex_data(),
        EC_KEY_OpenSSL(), EC_KEY_set_ex_data(), EC_KEY_set_default_method(),
        EC_KEY_METHOD_*(), EC_KEY_set_method()

        See "Providers are a replacement for engines and low-level method
        overrides"

    *   EC_METHOD_get_field_type()

        Use EC_GROUP_get_field_type(3) instead. See "Providers are a
        replacement for engines and low-level method overrides"

    *   EC_KEY_key2buf(), EC_KEY_oct2key(), EC_KEY_oct2priv(),
        EC_KEY_priv2buf(), EC_KEY_priv2oct()

        There are no replacements for these.

    *   EC_KEY_new(), EC_KEY_new_by_curve_name(), EC_KEY_free(),
        EC_KEY_up_ref()

        See "Deprecated low-level object creation"

    *   EC_KEY_print(), EC_KEY_print_fp()

        See "Deprecated low-level key printing functions"

    *   EC_KEY_set_asn1_flag(), EC_KEY_set_conv_form(),
        EC_KEY_set_enc_flags()

        See "Deprecated low-level key parameter setters".

    *   EC_KEY_set_group(), EC_KEY_set_private_key(),
        EC_KEY_set_public_key(), EC_KEY_set_public_key_affine_coordinates()

        See "Deprecated low-level key parameter setters".

    *   ECParameters_print(), ECParameters_print_fp(),
        ECPKParameters_print(), ECPKParameters_print_fp()

        See "Deprecated low-level key printing functions"

    *   EC_POINT_bn2point(), EC_POINT_point2bn()

        These functions were not particularly useful, since EC point
        serialization formats are not individual big-endian integers.

    *   EC_POINT_get_affine_coordinates_GF2m(),
        EC_POINT_get_affine_coordinates_GFp(),
        EC_POINT_set_affine_coordinates_GF2m(),
        EC_POINT_set_affine_coordinates_GFp()

        Applications should use EC_POINT_get_affine_coordinates(3) and
        EC_POINT_set_affine_coordinates(3) instead.

    *   EC_POINT_get_Jprojective_coordinates_GFp(),
        EC_POINT_set_Jprojective_coordinates_GFp()

        These functions are not widely used. Applications should instead use
        the EC_POINT_set_affine_coordinates(3) and
        EC_POINT_get_affine_coordinates(3) functions.

    *   EC_POINT_make_affine(), EC_POINTs_make_affine()

        There is no replacement. These functions were not widely used, and
        OpenSSL automatically performs this conversion when needed.

    *   EC_POINT_set_compressed_coordinates_GF2m(),
        EC_POINT_set_compressed_coordinates_GFp()

        Applications should use EC_POINT_set_compressed_coordinates(3)
        instead.

    *   EC_POINTs_mul()

        This function is not widely used. Applications should instead use
        the EC_POINT_mul(3) function.

    *   ENGINE_*()

        All engine functions are deprecated. An engine should be rewritten
        as a provider. See "Providers are a replacement for engines and
        low-level method overrides".

    *   ERR_load_*(), ERR_func_error_string(), ERR_get_error_line(),
        ERR_get_error_line_data(), ERR_get_state()

        OpenSSL now loads error strings automatically so these functions are
        not needed.

    *   ERR_peek_error_line_data(), ERR_peek_last_error_line_data()

        The new functions are ERR_peek_error_func(3),
        ERR_peek_last_error_func(3), ERR_peek_error_data(3),
        ERR_peek_last_error_data(3), ERR_get_error_all(3),
        ERR_peek_error_all(3) and ERR_peek_last_error_all(3). Applications
        should use ERR_get_error_all(3), or pick information with ERR_peek
        functions and finish off with getting the error code by using
        ERR_get_error(3).

    *   EVP_CIPHER_CTX_iv(), EVP_CIPHER_CTX_iv_noconst(),
        EVP_CIPHER_CTX_original_iv()

        Applications should instead use EVP_CIPHER_CTX_get_updated_iv(3),
        EVP_CIPHER_CTX_get_updated_iv(3) and
        EVP_CIPHER_CTX_get_original_iv(3) respectively. See
        EVP_CIPHER_CTX_get_original_iv(3) for further information.

    *   EVP_CIPHER_meth_*(), EVP_MD_CTX_set_update_fn(),
        EVP_MD_CTX_update_fn(), EVP_MD_meth_*()

        See "Providers are a replacement for engines and low-level method
        overrides".

    *   EVP_PKEY_CTRL_PKCS7_ENCRYPT(), EVP_PKEY_CTRL_PKCS7_DECRYPT(),
        EVP_PKEY_CTRL_PKCS7_SIGN(), EVP_PKEY_CTRL_CMS_ENCRYPT(),
        EVP_PKEY_CTRL_CMS_DECRYPT(), and EVP_PKEY_CTRL_CMS_SIGN()

        These control operations are not invoked by the OpenSSL library
        anymore and are replaced by direct checks of the key operation
        against the key type when the operation is initialized.

    *   EVP_PKEY_CTX_get0_dh_kdf_ukm(), EVP_PKEY_CTX_get0_ecdh_kdf_ukm()

        See the "kdf-ukm" item in "DH key exchange parameters" in
        EVP_KEYEXCH-DH(7) and "ECDH Key Exchange parameters" in
        EVP_KEYEXCH-ECDH(7). These functions are obsolete and should not be
        required.

    *   EVP_PKEY_CTX_set_rsa_keygen_pubexp()

        Applications should use EVP_PKEY_CTX_set1_rsa_keygen_pubexp(3)
        instead.

    *   EVP_PKEY_cmp(), EVP_PKEY_cmp_parameters()

        Applications should use EVP_PKEY_eq(3) and EVP_PKEY_parameters_eq(3)
        instead. See EVP_PKEY_copy_parameters(3) for further details.

    *   EVP_PKEY_encrypt_old(), EVP_PKEY_decrypt_old(),

        Applications should use EVP_PKEY_encrypt_init(3) and
        EVP_PKEY_encrypt(3) or EVP_PKEY_decrypt_init(3) and
        EVP_PKEY_decrypt(3) instead.

    *   EVP_PKEY_get0()

        This function returns NULL if the key comes from a provider.

    *   EVP_PKEY_get0_DH(), EVP_PKEY_get0_DSA(), EVP_PKEY_get0_EC_KEY(),
        EVP_PKEY_get0_RSA(), EVP_PKEY_get1_DH(), EVP_PKEY_get1_DSA(),
        EVP_PKEY_get1_EC_KEY and EVP_PKEY_get1_RSA(), EVP_PKEY_get0_hmac(),
        EVP_PKEY_get0_poly1305(), EVP_PKEY_get0_siphash()

        See "Functions that return an internal key should be treated as read
        only".

    *   EVP_PKEY_meth_*()

        See "Providers are a replacement for engines and low-level method
        overrides".

    *   EVP_PKEY_new_CMAC_key()

        See "Deprecated low-level MAC functions".

    *   EVP_PKEY_assign(), EVP_PKEY_set1_DH(), EVP_PKEY_set1_DSA(),
        EVP_PKEY_set1_EC_KEY(), EVP_PKEY_set1_RSA()

        See "Deprecated low-level key object getters and setters"

    *   EVP_PKEY_set1_tls_encodedpoint() EVP_PKEY_get1_tls_encodedpoint()

        These functions were previously used by libssl to set or get an
        encoded public key into/from an EVP_PKEY object. With OpenSSL 3.0
        these are replaced by the more generic functions
        EVP_PKEY_set1_encoded_public_key(3) and
        EVP_PKEY_get1_encoded_public_key(3). The old versions have been
        converted to deprecated macros that just call the new functions.

    *   EVP_PKEY_set1_engine(), EVP_PKEY_get0_engine()

        See "Providers are a replacement for engines and low-level method
        overrides".

    *   EVP_PKEY_set_alias_type()

        This function has been removed. There is no replacement. See
        "EVP_PKEY_set_alias_type() method has been removed"

    *   HMAC_Init_ex(), HMAC_Update(), HMAC_Final(), HMAC_size()

        See "Deprecated low-level MAC functions".

    *   HMAC_CTX_new(), HMAC_CTX_free(), HMAC_CTX_copy(), HMAC_CTX_reset(),
        HMAC_CTX_set_flags(), HMAC_CTX_get_md()

        See "Deprecated low-level MAC functions".

    *   i2d_DHparams(), i2d_DHxparams()

        See "Deprecated low-level key reading and writing functions" and
        "Migration" in d2i_RSAPrivateKey(3)

    *   i2d_DSAparams(), i2d_DSAPrivateKey(), i2d_DSAPrivateKey_bio(),
        i2d_DSAPrivateKey_fp(), i2d_DSA_PUBKEY(), i2d_DSA_PUBKEY_bio(),
        i2d_DSA_PUBKEY_fp(), i2d_DSAPublicKey()

        See "Deprecated low-level key reading and writing functions" and
        "Migration" in d2i_RSAPrivateKey(3)

    *   i2d_ECParameters(), i2d_ECPrivateKey(), i2d_ECPrivateKey_bio(),
        i2d_ECPrivateKey_fp(), i2d_EC_PUBKEY(), i2d_EC_PUBKEY_bio(),
        i2d_EC_PUBKEY_fp()

        See "Deprecated low-level key reading and writing functions" and
        "Migration" in d2i_RSAPrivateKey(3)

    *   i2o_ECPublicKey()

        Use EVP_PKEY_get1_encoded_public_key(3). See "Deprecated low-level
        key parameter getters"

    *   i2d_RSAPrivateKey(), i2d_RSAPrivateKey_bio(),
        i2d_RSAPrivateKey_fp(), i2d_RSA_PUBKEY(), i2d_RSA_PUBKEY_bio(),
        i2d_RSA_PUBKEY_fp(), i2d_RSAPublicKey(), i2d_RSAPublicKey_bio(),
        i2d_RSAPublicKey_fp()

        See "Deprecated low-level key reading and writing functions" and
        "Migration" in d2i_RSAPrivateKey(3)

    *   IDEA_encrypt(), IDEA_set_decrypt_key(), IDEA_set_encrypt_key(),
        IDEA_cbc_encrypt(), IDEA_cfb64_encrypt(), IDEA_ecb_encrypt(),
        IDEA_ofb64_encrypt()

        See "Deprecated low-level encryption functions". IDEA has been moved
        to the Legacy Provider.

    *   IDEA_options()

        There is no replacement. This function returned a constant string.

    *   MD2(), MD2_Init(), MD2_Update(), MD2_Final()

        See "Deprecated low-level encryption functions". MD2 has been moved
        to the Legacy Provider.

    *   MD2_options()

        There is no replacement. This function returned a constant string.

    *   MD4(), MD4_Init(), MD4_Update(), MD4_Final(), MD4_Transform()

        See "Deprecated low-level encryption functions". MD4 has been moved
        to the Legacy Provider.

    *   MDC2(), MDC2_Init(), MDC2_Update(), MDC2_Final()

        See "Deprecated low-level encryption functions". MDC2 has been moved
        to the Legacy Provider.

    *   MD5(), MD5_Init(), MD5_Update(), MD5_Final(), MD5_Transform()

        See "Deprecated low-level encryption functions".

    *   NCONF_WIN32()

        This undocumented function has no replacement. See "HISTORY" in
        config(5) for more details.

    *   OCSP_parse_url()

        Use OSSL_HTTP_parse_url(3) instead.

    *   OCSP_REQ_CTX type and OCSP_REQ_CTX_*() functions

        These methods were used to collect all necessary data to form a HTTP
        request, and to perform the HTTP transfer with that request. With
        OpenSSL 3.0, the type is OSSL_HTTP_REQ_CTX, and the deprecated
        functions are replaced with OSSL_HTTP_REQ_CTX_*(). See
        OSSL_HTTP_REQ_CTX(3) for additional details.

    *   OPENSSL_fork_child(), OPENSSL_fork_parent(), OPENSSL_fork_prepare()

        There is no replacement for these functions. These pthread fork
        support methods were unused by OpenSSL.

    *   OSSL_STORE_ctrl(), OSSL_STORE_do_all_loaders(),
        OSSL_STORE_LOADER_get0_engine(), OSSL_STORE_LOADER_get0_scheme(),
        OSSL_STORE_LOADER_new(), OSSL_STORE_LOADER_set_attach(),
        OSSL_STORE_LOADER_set_close(), OSSL_STORE_LOADER_set_ctrl(),
        OSSL_STORE_LOADER_set_eof(), OSSL_STORE_LOADER_set_error(),
        OSSL_STORE_LOADER_set_expect(), OSSL_STORE_LOADER_set_find(),
        OSSL_STORE_LOADER_set_load(), OSSL_STORE_LOADER_set_open(),
        OSSL_STORE_LOADER_set_open_ex(), OSSL_STORE_register_loader(),
        OSSL_STORE_unregister_loader(), OSSL_STORE_vctrl()

        These functions helped applications and engines create loaders for
        schemes they supported. These are all deprecated and discouraged in
        favour of provider implementations, see provider-storemgmt(7).

    *   PEM_read_DHparams(), PEM_read_bio_DHparams(), PEM_read_DSAparams(),
        PEM_read_bio_DSAparams(), PEM_read_DSAPrivateKey(),
        PEM_read_DSA_PUBKEY(), PEM_read_bio_DSAPrivateKey and
        PEM_read_bio_DSA_PUBKEY(), PEM_read_ECPKParameters(),
        PEM_read_ECPrivateKey(), PEM_read_EC_PUBKEY(),
        PEM_read_bio_ECPKParameters(), PEM_read_bio_ECPrivateKey(),
        PEM_read_bio_EC_PUBKEY(), PEM_read_RSAPrivateKey(),
        PEM_read_RSA_PUBKEY(), PEM_read_RSAPublicKey(),
        PEM_read_bio_RSAPrivateKey(), PEM_read_bio_RSA_PUBKEY(),
        PEM_read_bio_RSAPublicKey(), PEM_write_bio_DHparams(),
        PEM_write_bio_DHxparams(), PEM_write_DHparams(),
        PEM_write_DHxparams(), PEM_write_DSAparams(),
        PEM_write_DSAPrivateKey(), PEM_write_DSA_PUBKEY(),
        PEM_write_bio_DSAparams(), PEM_write_bio_DSAPrivateKey(),
        PEM_write_bio_DSA_PUBKEY(), PEM_write_ECPKParameters(),
        PEM_write_ECPrivateKey(), PEM_write_EC_PUBKEY(),
        PEM_write_bio_ECPKParameters(), PEM_write_bio_ECPrivateKey(),
        PEM_write_bio_EC_PUBKEY(), PEM_write_RSAPrivateKey(),
        PEM_write_RSA_PUBKEY(), PEM_write_RSAPublicKey(),
        PEM_write_bio_RSAPrivateKey(), PEM_write_bio_RSA_PUBKEY(),
        PEM_write_bio_RSAPublicKey(),

        See "Deprecated low-level key reading and writing functions"

    *   PKCS1_MGF1()

        See "Deprecated low-level encryption functions".

    *   RAND_get_rand_method(), RAND_set_rand_method(), RAND_OpenSSL(),
        RAND_set_rand_engine()

        Applications should instead use RAND_set_DRBG_type(3), EVP_RAND(3)
        and EVP_RAND(7). See RAND_set_rand_method(3) for more details.

    *   RC2_encrypt(), RC2_decrypt(), RC2_set_key(), RC2_cbc_encrypt(),
        RC2_cfb64_encrypt(), RC2_ecb_encrypt(), RC2_ofb64_encrypt(), RC4(),
        RC4_set_key(), RC4_options(), RC5_32_encrypt(), RC5_32_set_key(),
        RC5_32_decrypt(), RC5_32_cbc_encrypt(), RC5_32_cfb64_encrypt(),
        RC5_32_ecb_encrypt(), RC5_32_ofb64_encrypt()

        See "Deprecated low-level encryption functions". The Algorithms
        "RC2", "RC4" and "RC5" have been moved to the Legacy Provider.

    *   RIPEMD160(), RIPEMD160_Init(), RIPEMD160_Update(),
        RIPEMD160_Final(), RIPEMD160_Transform()

        See "Deprecated low-level digest functions". The RIPE algorithm has
        been moved to the Legacy Provider.

    *   RSA_bits(), RSA_security_bits(), RSA_size()

        Use EVP_PKEY_get_bits(3), EVP_PKEY_get_security_bits(3) and
        EVP_PKEY_get_size(3).

    *   RSA_check_key(), RSA_check_key_ex()

        See "Deprecated low-level validation functions"

    *   RSA_clear_flags(), RSA_flags(), RSA_set_flags(), RSA_test_flags(),
        RSA_setup_blinding(), RSA_blinding_off(), RSA_blinding_on()

        All of these RSA flags have been deprecated without replacement:

        RSA_FLAG_BLINDING, RSA_FLAG_CACHE_PRIVATE, RSA_FLAG_CACHE_PUBLIC,
        RSA_FLAG_EXT_PKEY, RSA_FLAG_NO_BLINDING, RSA_FLAG_THREAD_SAFE
        RSA_METHOD_FLAG_NO_CHECK

    *   RSA_generate_key_ex(), RSA_generate_multi_prime_key()

        See "Deprecated low-level key generation functions".

    *   RSA_get0_engine()

        See "Providers are a replacement for engines and low-level method
        overrides"

    *   RSA_get0_crt_params(), RSA_get0_d(), RSA_get0_dmp1(),
        RSA_get0_dmq1(), RSA_get0_e(), RSA_get0_factors(), RSA_get0_iqmp(),
        RSA_get0_key(), RSA_get0_multi_prime_crt_params(),
        RSA_get0_multi_prime_factors(), RSA_get0_n(), RSA_get0_p(),
        RSA_get0_pss_params(), RSA_get0_q(),
        RSA_get_multi_prime_extra_count()

        See "Deprecated low-level key parameter getters"

    *   RSA_new(), RSA_free(), RSA_up_ref()

        See "Deprecated low-level object creation".

    *   RSA_get_default_method(), RSA_get_ex_data and RSA_get_method()

        See "Providers are a replacement for engines and low-level method
        overrides".

    *   RSA_get_version()

        There is no replacement.

    *   RSA_meth_*(), RSA_new_method(), RSA_null_method and
        RSA_PKCS1_OpenSSL()

        See "Providers are a replacement for engines and low-level method
        overrides".

    *   RSA_padding_add_*(), RSA_padding_check_*()

        See "Deprecated low-level signing functions" and "Deprecated
        low-level encryption functions".

    *   RSA_print(), RSA_print_fp()

        See "Deprecated low-level key printing functions"

    *   RSA_public_encrypt(), RSA_private_decrypt()

        See "Deprecated low-level encryption functions"

    *   RSA_private_encrypt(), RSA_public_decrypt()

        This is equivalent to doing sign and verify recover operations (with
        a padding mode of none). See "Deprecated low-level signing
        functions".

    *   RSAPrivateKey_dup(), RSAPublicKey_dup()

        There is no direct replacement. Applications may use
        EVP_PKEY_dup(3).

    *   RSAPublicKey_it(), RSAPrivateKey_it()

        See "Deprecated low-level key reading and writing functions"

    *   RSA_set0_crt_params(), RSA_set0_factors(), RSA_set0_key(),
        RSA_set0_multi_prime_params()

        See "Deprecated low-level key parameter setters".

    *   RSA_set_default_method(), RSA_set_method(), RSA_set_ex_data()

        See "Providers are a replacement for engines and low-level method
        overrides"

    *   RSA_sign(), RSA_sign_ASN1_OCTET_STRING(), RSA_verify(),
        RSA_verify_ASN1_OCTET_STRING(), RSA_verify_PKCS1_PSS(),
        RSA_verify_PKCS1_PSS_mgf1()

        See "Deprecated low-level signing functions".

    *   RSA_X931_derive_ex(), RSA_X931_generate_key_ex(), RSA_X931_hash_id()

        There are no replacements for these functions. X931 padding can be
        set using "Signature Parameters" in EVP_SIGNATURE-RSA(7). See
        OSSL_SIGNATURE_PARAM_PAD_MODE.

    *   SEED_encrypt(), SEED_decrypt(), SEED_set_key(), SEED_cbc_encrypt(),
        SEED_cfb128_encrypt(), SEED_ecb_encrypt(), SEED_ofb128_encrypt()

        See "Deprecated low-level encryption functions". The SEED algorithm
        has been moved to the Legacy Provider.

    *   SHA1_Init(), SHA1_Update(), SHA1_Final(), SHA1_Transform(),
        SHA224_Init(), SHA224_Update(), SHA224_Final(), SHA256_Init(),
        SHA256_Update(), SHA256_Final(), SHA256_Transform(), SHA384_Init(),
        SHA384_Update(), SHA384_Final(), SHA512_Init(), SHA512_Update(),
        SHA512_Final(), SHA512_Transform()

        See "Deprecated low-level digest functions".

    *   SRP_Calc_A(), SRP_Calc_B(), SRP_Calc_client_key(),
        SRP_Calc_server_key(), SRP_Calc_u(), SRP_Calc_x(),
        SRP_check_known_gN_param(), SRP_create_verifier(),
        SRP_create_verifier_BN(), SRP_get_default_gN(), SRP_user_pwd_free(),
        SRP_user_pwd_new(), SRP_user_pwd_set0_sv(), SRP_user_pwd_set1_ids(),
        SRP_user_pwd_set_gN(), SRP_VBASE_add0_user(), SRP_VBASE_free(),
        SRP_VBASE_get1_by_user(), SRP_VBASE_init(), SRP_VBASE_new(),
        SRP_Verify_A_mod_N(), SRP_Verify_B_mod_N()

        There are no replacements for the SRP functions.

    *   SSL_CTX_set_tmp_dh_callback(), SSL_set_tmp_dh_callback(),
        SSL_CTX_set_tmp_dh(), SSL_set_tmp_dh()

        These are used to set the Diffie-Hellman (DH) parameters that are to
        be used by servers requiring ephemeral DH keys. Instead applications
        should consider using the built-in DH parameters that are available
        by calling SSL_CTX_set_dh_auto(3) or SSL_set_dh_auto(3). If custom
        parameters are necessary then applications can use the alternative
        functions SSL_CTX_set0_tmp_dh_pkey(3) and SSL_set0_tmp_dh_pkey(3).
        There is no direct replacement for the "callback" functions. The
        callback was originally useful in order to have different parameters
        for export and non-export ciphersuites. Export ciphersuites are no
        longer supported by OpenSSL. Use of the callback functions should be
        replaced by one of the other methods described above.

    *   SSL_CTX_set_tlsext_ticket_key_cb()

        Use the new SSL_CTX_set_tlsext_ticket_key_evp_cb(3) function
        instead.

    *   WHIRLPOOL(), WHIRLPOOL_Init(), WHIRLPOOL_Update(),
        WHIRLPOOL_Final(), WHIRLPOOL_BitUpdate()

        See "Deprecated low-level digest functions". The Whirlpool algorithm
        has been moved to the Legacy Provider.

    *   X509_certificate_type()

        This was an undocumented function. Applications can use
        X509_get0_pubkey(3) and X509_get0_signature(3) instead.

    *   X509_http_nbio(), X509_CRL_http_nbio()

        Use X509_load_http(3) and X509_CRL_load_http(3) instead.

   NID handling for provided keys and algorithms
    The following functions for NID (numeric id) handling have changed
    semantics.

    *   EVP_PKEY_id(), EVP_PKEY_get_id()

        This function was previously used to reliably return the NID of an
        EVP_PKEY object, e.g., to look up the name of the algorithm of such
        EVP_PKEY by calling OBJ_nid2sn(3). With the introduction of
        provider(7)s EVP_PKEY_id() or its new equivalent EVP_PKEY_get_id(3)
        might now also return the value -1 (EVP_PKEY_KEYMGMT) indicating the
        use of a provider to implement the EVP_PKEY object. Therefore, the
        use of EVP_PKEY_get0_type_name(3) is recommended for retrieving the
        name of the EVP_PKEY algorithm.

  Using the FIPS Module in applications
    See fips_module(7) and OSSL_PROVIDER-FIPS(7) for details.

  OpenSSL command line application changes
   New applications
    openssl kdf uses the new EVP_KDF(3) API. openssl kdf uses the new
    EVP_MAC(3) API.

   Added options
    -provider_path and -provider are available to all apps and can be used
    multiple times to load any providers, such as the 'legacy' provider or
    third party providers. If used then the 'default' provider would also
    need to be specified if required. The -provider_path must be specified
    before the -provider option.

    The list app has many new options. See openssl-list(1) for more
    information.

    -crl_lastupdate and -crl_nextupdate used by openssl ca allows explicit
    setting of fields in the generated CRL.

   Removed options
    Interactive mode is not longer available.

    The -crypt option used by openssl passwd. The -c option used by openssl
    x509, openssl dhparam, openssl dsaparam, and openssl ecparam.

   Other Changes
    The output of Command line applications may have minor changes. These
    are primarily changes in capitalisation and white space. However, in
    some cases, there are additional differences. For example, the DH
    parameters output from openssl dhparam now lists 'P', 'Q', 'G' and
    'pcounter' instead of 'prime', 'generator', 'subgroup order' and
    'counter' respectively.

    The openssl commands that read keys, certificates, and CRLs now
    automatically detect the PEM or DER format of the input files so it is
    not necessary to explicitly specify the input format anymore. However if
    the input format option is used the specified format will be required.

    openssl speed no longer uses low-level API calls. This implies some of
    the performance numbers might not be comparable with the previous
    releases due to higher overhead. This applies particularly to measuring
    performance on smaller data chunks.

    b<openssl dhparam>, openssl dsa, openssl gendsa, openssl dsaparam,
    openssl genrsa and openssl rsa have been modified to use PKEY APIs.
    openssl genrsa and openssl rsa now write PKCS #8 keys by default.

   Default settings
    "SHA256" is now the default digest for TS query used by openssl ts.

   Deprecated apps
    openssl rsautl is deprecated, use openssl pkeyutl instead. openssl
    dhparam, openssl dsa, openssl gendsa, openssl dsaparam, openssl genrsa,
    openssl rsa, openssl genrsa and openssl rsa are now in maintenance mode
    and no new features will be added to them.

  TLS Changes
    *   TLS 1.3 FFDHE key exchange support added

        This uses DH safe prime named groups.

    *   Support for fully "pluggable" TLSv1.3 groups.

        This means that providers may supply their own group implementations
        (using either the "key exchange" or the "key encapsulation" methods)
        which will automatically be detected and used by libssl.

    *   SSL and SSL_CTX options are now 64 bit instead of 32 bit.

        The signatures of the functions to get and set options on SSL and
        SSL_CTX objects changed from "unsigned long" to "uint64_t" type.

        This may require source code changes. For example it is no longer
        possible to use the SSL_OP_ macro values in preprocessor "#if"
        conditions. However it is still possible to test whether these
        macros are defined or not.

        See SSL_CTX_get_options(3), SSL_CTX_set_options(3),
        SSL_get_options(3) and SSL_set_options(3).

    *   SSL_set1_host() and SSL_add1_host() Changes

        These functions now take IP literal addresses as well as actual
        hostnames.

    *   Added SSL option SSL_OP_CLEANSE_PLAINTEXT

        If the option is set, openssl cleanses (zeroizes) plaintext bytes
        from internal buffers after delivering them to the application.
        Note, the application is still responsible for cleansing other
        copies (e.g.: data received by SSL_read(3)).

    *   Client-initiated renegotiation is disabled by default.

        To allow it, use the -client_renegotiation option, the
        SSL_OP_ALLOW_CLIENT_RENEGOTIATION flag, or the "ClientRenegotiation"
        config parameter as appropriate.

    *   Secure renegotiation is now required by default for TLS connections

        Support for RFC 5746 secure renegotiation is now required by default
        for SSL or TLS connections to succeed. Applications that require the
        ability to connect to legacy peers will need to explicitly set
        SSL_OP_LEGACY_SERVER_CONNECT. Accordingly,
        SSL_OP_LEGACY_SERVER_CONNECT is no longer set as part of SSL_OP_ALL.

    *   Combining the Configure options no-ec and no-dh no longer disables
        TLSv1.3

        Typically if OpenSSL has no EC or DH algorithms then it cannot
        support connections with TLSv1.3. However OpenSSL now supports
        "pluggable" groups through providers. Therefore third party
        providers may supply group implementations even where there are no
        built-in ones. Attempting to create TLS connections in such a build
        without also disabling TLSv1.3 at run time or using third party
        provider groups may result in handshake failures. TLSv1.3 can be
        disabled at compile time using the "no-tls1_3" Configure option.

    *   SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() changes.

        The methods now ignore unknown ciphers.

    *   Security callback change.

        The security callback, which can be customised by application code,
        supports the security operation SSL_SECOP_TMP_DH. This is defined to
        take an EVP_PKEY in the "other" parameter. In most places this is
        what is passed. All these places occur server side. However there
        was one client side call of this security operation and it passed a
        DH object instead. This is incorrect according to the definition of
        SSL_SECOP_TMP_DH, and is inconsistent with all of the other
        locations. Therefore this client side call has been changed to pass
        an EVP_PKEY instead.

    *   New SSL option SSL_OP_IGNORE_UNEXPECTED_EOF

        The SSL option SSL_OP_IGNORE_UNEXPECTED_EOF is introduced. If that
        option is set, an unexpected EOF is ignored, it pretends a close
        notify was received instead and so the returned error becomes
        SSL_ERROR_ZERO_RETURN.

    *   The security strength of SHA1 and MD5 based signatures in TLS has
        been reduced.

        This results in SSL 3, TLS 1.0, TLS 1.1 and DTLS 1.0 no longer
        working at the default security level of 1 and instead requires
        security level 0. The security level can be changed either using the
        cipher string with @SECLEVEL, or calling
        SSL_CTX_set_security_level(3). This also means that where the
        signature algorithms extension is missing from a ClientHello then
        the handshake will fail in TLS 1.2 at security level 1. This is
        because, although this extension is optional, failing to provide one
        means that OpenSSL will fallback to a default set of signature
        algorithms. This default set requires the availability of SHA1.

    *   X509 certificates signed using SHA1 are no longer allowed at
        security level 1 and above.

        In TLS/SSL the default security level is 1. It can be set either
        using the cipher string with @SECLEVEL, or calling
        SSL_CTX_set_security_level(3). If the leaf certificate is signed
        with SHA-1, a call to SSL_CTX_use_certificate(3) will fail if the
        security level is not lowered first. Outside TLS/SSL, the default
        security level is -1 (effectively 0). It can be set using
        X509_VERIFY_PARAM_set_auth_level(3) or using the -auth_level options
        of the commands.

SEE ALSO
    fips_module(7)

HISTORY
    The migration guide was created for OpenSSL 3.0.

COPYRIGHT
    Copyright 2021-2025 The OpenSSL Project Authors. All Rights Reserved.

    Licensed under the Apache License 2.0 (the "License"). You may not use
    this file except in compliance with the License. You can obtain a copy
    in the file LICENSE in the source distribution or at
    <https://www.openssl.org/source/license.html>.

