This call is made to set the expected B<CCM> tag value when decrypting or
the length of the tag (with the C<tag> parameter set to NULL) when encrypting.
The tag length is often referred to as B<M>. If not set a default value is
-used (12 for AES).
+used (12 for AES). When decrypting, the tag needs to be set before passing
+in data to be decrypted, but as in GCM and OCB mode, it can be set after
+passing additional authenticated data (see L<AEAD Interface>).
=item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
Sets the nonce length. This call can only be made before specifying the nonce.
If not called a default nonce length of 12 (i.e. 96 bits) is used. The maximum
-nonce length is 16 (B<CHACHA_CTR_SIZE>, i.e. 128-bits).
+nonce length is 12 bytes (i.e. 96-bits). If a nonce of less than 12 bytes is set
+then the nonce is automatically padded with leading 0 bytes to make it 12 bytes
+in length.
=item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)