Commit 12bbae8b authored by Niels Möller's avatar Niels Möller

Stress that the salsa20 hash function is not for general use.

parent 90320ba2
2012-09-21 Niels Möller <nisse@lysator.liu.se>
* nettle.texinfo (Cipher functions): Stress that the salsa20 hash
function is not suitable as a general hash function.
2012-09-20 Simon Josefsson <simon@josefsson.org> 2012-09-20 Simon Josefsson <simon@josefsson.org>
* pbkdf2-hmac-sha1.c, pbkdf2-hmac-sha256.c: New files. * pbkdf2-hmac-sha1.c, pbkdf2-hmac-sha256.c: New files.
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...@@ -1275,12 +1275,15 @@ in this way to ridicule United States export restrictions which treated hash ...@@ -1275,12 +1275,15 @@ in this way to ridicule United States export restrictions which treated hash
functions as nice and harmless, but ciphers as dangerous munitions. functions as nice and harmless, but ciphers as dangerous munitions.
Salsa20 uses the same idea, but with a new specialized hash function to Salsa20 uses the same idea, but with a new specialized hash function to
mix key, block counter, and a couple of constants (input and output are mix key, block counter, and a couple of constants. It's also designed
the same size, making it not directly applicable for use as a general for speed; on x86_64, it is currently the fastest cipher offered by
hash function). It's also designed for speed; on x86_64, it is currently nettle. It uses a block size of 512 bits (64 octets) and there are two
the fastest cipher offered by nettle. It uses a block size of 512 bits specified key sizes, 128 and 256 bits (16 and 32 octets).
(64 octets) and there are two specified key sizes, 128 and 256 bits (16
and 32 octets). @strong{Caution:} The hash function used in Salsa20 is @emph{not}
directly applicable for use as a general hash function. It's @emph{not}
collision resistant if arbitrary inputs are allowed, and furthermore,
the input and output is of fixed size.
When using Salsa20 to process a message, one specifies both a key and a When using Salsa20 to process a message, one specifies both a key and a
@dfn{nonce}, the latter playing a similar rôle to the initialization @dfn{nonce}, the latter playing a similar rôle to the initialization
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