Cryptography and SSL/TLS Toolkit



EVP_MD-BLAKE2 - The BLAKE2 EVP_MD implementation


Support for computing BLAKE2 digests through the EVP_MD API.


This implementation is only available with the default provider, and includes the following varieties:


Known names are "BLAKE2S-256" and "BLAKE2s256".


Known names are "BLAKE2B-512" and "BLAKE2b512".

Settable Parameters

"BLAKE2B-512" supports the following EVP_MD_CTX_set_params() key described in "PARAMETERS" in EVP_DigestInit(3).

"xoflen" (OSSL_DIGEST_PARAM_XOFLEN) <unsigned integer>

Gettable Parameters

This implementation supports the common gettable parameters described in EVP_MD-common(7).

Settable Context Parameters

The implementation supports the following OSSL_PARAM(3) entries which are settable for an EVP_MD_CTX with EVP_DigestInit_ex2(3) or EVP_MD_CTX_set_params(3):

"size" (OSSL_DIGEST_PARAM_SIZE) <unsigned integer>

Sets a different digest length for the EVP_DigestFinal(3) output. The value of the "size" parameter must not exceed the default digest length of the respective BLAKE2 algorithm variants, 64 for BLAKE2B-512 and 32 for BLAKE2S-256. The parameter must be set with the EVP_DigestInit_ex2(3) call to have an immediate effect. When set with EVP_MD_CTX_set_params(3) it will have an effect only if the EVP_MD_CTX context is reinitialized.


provider-digest(7), OSSL_PROVIDER-default(7)


This functionality was added in OpenSSL 3.0.

The variable size support was added in OpenSSL 3.2 for BLAKE2B-512 and in OpenSSL 3.3 for BLAKE2S-256.

Copyright 2020-2022 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