Cryptography and SSL/TLS Toolkit



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


See the individual manual pages for details.


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 For an overview of some of the key concepts introduced in OpenSSL 3.0 see crypto(7).


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

There are no other changes requiring additional migration measures since 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 (both licenses apply). From OpenSSL 3.0 this is replaced by the Apache License v2.

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:


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 4210)

This also covers CRMF (RFC 4211) and HTTP transfer (RFC 6712) 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 then 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 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 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 */

    The code needs to be amended to look like this:

    EVP_MD_CTX *md_ctx;
    md_ctx = EVP_MD_CTX_new();
  3. Support for TLSv1.3 has been added.

    This has a number of implications for SSL/TLS applications. See the TLS1.3 page 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.

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 file.


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.

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.


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), l<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), "DH parameters" in EVP_PKEY-DH(7), "DSA parameters" in EVP_PKEY-DSA(7), "FFC parameters" in EVP_PKEY-FFC(7), "Common EC parameters" in EVP_PKEY-EC(7) and "Common X25519, X448, ED25519 and ED448 parameters" in EVP_PKEY-X25519(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 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.

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.


    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.


    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.




The migration guide was created for OpenSSL 3.0.

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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