Commit ca1ffaf8 authored by Niels Möller's avatar Niels Möller

Document ChaCha.

parent 0a68c384
......@@ -2,6 +2,7 @@
* nettle.texinfo (DSA): Document new DSA interface.
(Salsa20): Update salsa20 docs.
(ChaCha): Document ChaCha.
2014-05-03 Niels Möller <nisse@lysator.liu.se>
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......@@ -1463,6 +1463,46 @@ in any other way.
Analogous to @code{cast128_encrypt}
@end deftypefun
@subsection ChaCha
ChaCha is a variant of the stream cipher Salsa20, also designed by D. J.
Bernstein. For more information on Salsa20, see below. Nettle defines
Chacha in @file{<nettle/chacha.h>}.
@deftp {Context struct} {struct chacha_ctx}
@end deftp
@defvr Constant CHACHA_KEY_SIZE
ChaCha key size, 32.
@end defvr
@defvr Constant CHACHA_BLOCK_SIZE
ChaCha block size, 64.
@end defvr
@defvr Constant CHACHA_NONCE_SIZE
Size of the nonce, 8.
@end defvr
@deftypefun void chacha_set_key (struct chacha_ctx *@var{ctx}, const uint8_t *@var{key})
Initialize the cipher. The same function is used for both encryption and
decryption. Before using the cipher,
you @emph{must} also call @code{chacha_set_nonce}, see below.
@end deftypefun
@deftypefun void chacha_set_nonce (struct chacha_ctx *@var{ctx}, const uint8_t *@var{nonce})
Sets the nonce. It is always of size @code{CHACHA_NONCE_SIZE}, 8
octets. This function also initializes the block counter, setting it to
zero.
@end deftypefun
@deftypefun void chacha_crypt (struct chacha_ctx *@var{ctx}, size_t @var{length}, uint8_t *@var{dst}, const uint8_t *@var{src})
Encrypts or decrypts the data of a message, using ChaCha. When a
message is encrypted using a sequence of calls to @code{chacha_crypt},
all but the last call @emph{must} use a length that is a multiple of
@code{CHACHA_BLOCK_SIZE}.
@end deftypefun
@subsection DES
DES is the old Data Encryption Standard, specified by NIST. It uses a
block size of 64 bits (8 octets), and a key size of 56 bits. However,
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