diff --git a/ChangeLog b/ChangeLog index d5b2e2ff63ed3f316ed73ba3f0c47395524b6292..aa3bbfc0fa11589ee7f038ce2731254f5670ce85 100644 --- a/ChangeLog +++ b/ChangeLog @@ -8,6 +8,7 @@ * testsuite/shake.awk: New script to extract test vectors. * testsuite/Makefile.in (TS_NETTLE_SOURCES): Add shake256-test.c. (DISTFILES): Add shake.awk. + * nettle.texinfo (Recommended hash functions): Document SHAKE-256. * sha3.c (_sha3_pad): Generalized with an argument for the magic suffix defining the sha3 instance. diff --git a/nettle.texinfo b/nettle.texinfo index 5eb5752dc7af94012e0cebfc9f77d55591846491..2df85e77faf9fe00725d4ed4d90e4e462a5a1dff 100644 --- a/nettle.texinfo +++ b/nettle.texinfo @@ -834,6 +834,28 @@ octets of the digest are written. This function also resets the context. @end deftypefun +@subsubsection @acronym{SHAKE-256} +@cindex SHAKE + +In addition to those SHA-3 hash functions, Nettle also provides a SHA-3 +extendable-output function (XOF), SHAKE-256. Unlike SHA-3 hash functions, +SHAKE can produce an output digest of any desired length. + +To use SHAKE256, the context struct, init and update functions are the +same as for SHA3-256. To get a SHAKE256 digest, the following function +is used instead of @code{sha3_256_digest}. For an output size of +@code{SHA3_256_DIGEST_SIZE}, security is equivalent to SHA3-256 (but the +digest is different). Increasing output size further does not increase +security in terms of collision or preimage resistance. It can be seen as +a built in pseudorandomness generator. + +@deftypefun void sha3_256_shake (struct shake256_ctx *@var{ctx}, size_t @var{length}, uint8_t *@var{digest}) +Performs final processing and produces a SHAKE256 digest, writing it +to @var{digest}. @var{length} can be of arbitrary size. + +This function also resets the context. +@end deftypefun + @node Legacy hash functions, nettle_hash abstraction, Recommended hash functions, Hash functions @comment node-name, next, previous, up @subsection Legacy hash functions