diff options
| -rw-r--r-- | doc/man3/EVP_EncryptInit.pod | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/doc/man3/EVP_EncryptInit.pod b/doc/man3/EVP_EncryptInit.pod index 0d8a780bb7..ffd1aab2b3 100644 --- a/doc/man3/EVP_EncryptInit.pod +++ b/doc/man3/EVP_EncryptInit.pod @@ -380,18 +380,20 @@ B<EVP_CTRL_AEAD_SET_TAG>. =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag) -Sets the expected tag to C<taglen> bytes from C<tag>. -The tag length can only be set before specifying an IV. +When decrypting, this call sets the expected tag to C<taglen> bytes from C<tag>. C<taglen> must be between 1 and 16 inclusive. +The tag must be set prior to any call to EVP_DecryptFinal() or +EVP_DecryptFinal_ex(). For GCM, this call is only valid when decrypting data. For OCB, this call is valid when decrypting data to set the expected tag, -and before encryption to set the desired tag length. +and when encrypting to set the desired tag length. -In OCB mode, calling this before encryption with C<tag> set to C<NULL> sets the -tag length. If this is not called prior to encryption, a default tag length is -used. +In OCB mode, calling this when encrypting with C<tag> set to C<NULL> sets the +tag length. The tag length can only be set before specifying an IV. If this is +not called prior to setting the IV during encryption, then a default tag length +is used. For OCB AES, the default tag length is 16 (i.e. 128 bits). It is also the maximum tag length for OCB. |