diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/gcrypt.texi | 39 |
1 files changed, 31 insertions, 8 deletions
diff --git a/doc/gcrypt.texi b/doc/gcrypt.texi index 7337db95..8683ca88 100644 --- a/doc/gcrypt.texi +++ b/doc/gcrypt.texi @@ -1650,7 +1650,14 @@ mode, which can be used with ChaCha20 and Salsa20 stream ciphers. @item GCRY_CIPHER_MODE_OCB @cindex OCB, OCB3 OCB is an Authenticated Encryption with Associated Data (AEAD) block -cipher mode, which is specified in RFC-7253. +cipher mode, which is specified in RFC-7253. Supported tag lengths +are 128, 96, and 64 bit with the default being 128 bit. To switch to +a different tag length @code{gcry_cipher_ctl} using the command +@code{GCRYCTL_SET_TAGLEN} and the address of an @code{int} variable +set to 12 (for 96 bit) or 8 (for 64 bit) provided for the +@code{buffer} argument and @code{sizeof(int)} for @code{buflen}. + +Note that the use of @code{gcry_cipher_final} is required. @end table @@ -1750,12 +1757,9 @@ vector is passed as the buffer @var{K} of length @var{l} bytes and copied to internal data structures. The function checks that the IV matches the requirement of the selected algorithm and mode. -This function is also used with Salsa20 and ChaCha20 stream ciphers -to set or update the required nonce. In this case it needs to be -called after setting the key. - -This function is also used with the AEAD cipher modes to set or -update the required nonce. +This function is also used by AEAD modes and with Salsa20 and ChaCha20 +stream ciphers to set or update the required nonce. In these cases it +needs to be called after setting the key. @end deftypefun @@ -1827,6 +1831,9 @@ is sufficient space. Note that overlapping buffers are not allowed. Depending on the selected algorithms and encryption mode, the length of the buffers must be a multiple of the block size. +Some encryption modes require that @code{gcry_cipher_final} is used +before the final data chunk is passed to this function. + The function returns @code{0} on success or an error code. @end deftypefun @@ -1847,11 +1854,27 @@ is sufficient space. Note that overlapping buffers are not allowed. Depending on the selected algorithms and encryption mode, the length of the buffers must be a multiple of the block size. +Some encryption modes require that @code{gcry_cipher_final} is used +before the final data chunk is passed to this function. + The function returns @code{0} on success or an error code. @end deftypefun -OpenPGP (as defined in RFC-2440) requires a special sync operation in +The OCB mode features integrated padding and must thus be told about +the end of the input data. This is done with: + +@deftypefun gcry_error_t gcry_cipher_final (gcry_cipher_hd_t @var{h}) + +Set a flag in the context to tell the encrypt and decrypt functions +that their next call will provide the last chunk of data. Only the +first call to this function has an effect and only for modes which +support it. Checking the error in in general not necessary. This is +implemented as a macro. +@end deftypefun + + +OpenPGP (as defined in RFC-4880) requires a special sync operation in some places. The following function is used for this: @deftypefun gcry_error_t gcry_cipher_sync (gcry_cipher_hd_t @var{h}) |