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| -rw-r--r-- | doc/man3/EVP_MAC.pod | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/doc/man3/EVP_MAC.pod b/doc/man3/EVP_MAC.pod index 56ac92a486..762c0175ff 100644 --- a/doc/man3/EVP_MAC.pod +++ b/doc/man3/EVP_MAC.pod @@ -145,6 +145,9 @@ the key. If I<key> is NULL, the key must be set via I<params> either as part of this call or separately using EVP_MAC_CTX_set_params(). Providing non-NULL I<params> to this function is equivalent to calling EVP_MAC_CTX_set_params() with those I<params> for the same I<ctx> beforehand. +Note: There are additional requirements for some MAC algorithms during +re-initalization (i.e. calling EVP_MAC_init() on an EVP_MAC after EVP_MAC_final() +has been called on the same object). See the NOTES section below. EVP_MAC_init() should be called before EVP_MAC_update() and EVP_MAC_final(). @@ -342,6 +345,13 @@ not be considered a breaking change to the API. The usage of the parameter names "custom", "iv" and "salt" correspond to the names used in the standard where the algorithm was defined. +Some MAC algorithms store internal state that cannot be extracted during +re-initalization. For example GMAC cannot extract an B<IV> from the +underlying CIPHER context, and so calling EVP_MAC_init() on an EVP_MAC object +after EVP_MAC_final() has been called cannot reset its cipher state to what it +was when the B<IV> was initially generated. For such instances, an +B<OSSL_MAC_PARAM_IV> parameter must be passed with each call to EVP_MAC_init(). + =head1 RETURN VALUES EVP_MAC_fetch() returns a pointer to a newly fetched B<EVP_MAC>, or |