David Leon Gil
4ed45ec682
Speedup of about 1.4x on x64. Added benchmarks that use the ShakeHash interface, which doesn't require copying the state. Unaligned or generic xorIn and copyOut functions chosen via buildline, but both are tested. Substantial contributions from Eric Eisner. See golang.org/cl/151630044 for the previous CR. (There are also some minor edits/additions to the documentation.) Change-Id: I9500c25682457c82487512b9b8c66df7d75bff5d Reviewed-on: https://go-review.googlesource.com/2132 Reviewed-by: Adam Langley <agl@golang.org>
67 lines
3.1 KiB
Go
67 lines
3.1 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Package sha3 implements the SHA-3 fixed-output-length hash functions and
|
|
// the SHAKE variable-output-length hash functions defined by FIPS-202.
|
|
//
|
|
// Both types of hash function use the "sponge" construction and the Keccak
|
|
// permutation. For a detailed specification see http://keccak.noekeon.org/
|
|
//
|
|
//
|
|
// Guidance
|
|
//
|
|
// If you aren't sure what function you need, use SHAKE256 with at least 64
|
|
// bytes of output. The SHAKE instances are faster than the SHA3 instances;
|
|
// the latter have to allocate memory to conform to the hash.Hash interface.
|
|
//
|
|
// If you need a secret-key MAC (message authentication code), prepend the
|
|
// secret key to the input, hash with SHAKE256 and read at least 32 bytes of
|
|
// output.
|
|
//
|
|
//
|
|
// Security strengths
|
|
//
|
|
// The SHA3-x (x equals 224, 256, 384, or 512) functions have a security
|
|
// strength against preimage attacks of x bits. Since they only produce "x"
|
|
// bits of output, their collision-resistance is only "x/2" bits.
|
|
//
|
|
// The SHAKE-256 and -128 functions have a generic security strength of 256 and
|
|
// 128 bits against all attacks, provided that at least 2x bits of their output
|
|
// is used. Requesting more than 64 or 32 bytes of output, respectively, does
|
|
// not increase the collision-resistance of the SHAKE functions.
|
|
//
|
|
//
|
|
// The sponge construction
|
|
//
|
|
// A sponge builds a pseudo-random function from a public pseudo-random
|
|
// permutation, by applying the permutation to a state of "rate + capacity"
|
|
// bytes, but hiding "capacity" of the bytes.
|
|
//
|
|
// A sponge starts out with a zero state. To hash an input using a sponge, up
|
|
// to "rate" bytes of the input are XORed into the sponge's state. The sponge
|
|
// is then "full" and the permutation is applied to "empty" it. This process is
|
|
// repeated until all the input has been "absorbed". The input is then padded.
|
|
// The digest is "squeezed" from the sponge in the same way, except that output
|
|
// output is copied out instead of input being XORed in.
|
|
//
|
|
// A sponge is parameterized by its generic security strength, which is equal
|
|
// to half its capacity; capacity + rate is equal to the permutation's width.
|
|
// Since the KeccakF-1600 permutation is 1600 bits (200 bytes) wide, this means
|
|
// that the security strength of a sponge instance is equal to (1600 - bitrate) / 2.
|
|
//
|
|
//
|
|
// Recommendations
|
|
//
|
|
// The SHAKE functions are recommended for most new uses. They can produce
|
|
// output of arbitrary length. SHAKE256, with an output length of at least
|
|
// 64 bytes, provides 256-bit security against all attacks. The Keccak team
|
|
// recommends it for most applications upgrading from SHA2-512. (NIST chose a
|
|
// much stronger, but much slower, sponge instance for SHA3-512.)
|
|
//
|
|
// The SHA-3 functions are "drop-in" replacements for the SHA-2 functions.
|
|
// They produce output of the same length, with the same security strengths
|
|
// against all attacks. This means, in particular, that SHA3-256 only has
|
|
// 128-bit collision resistance, because its output length is 32 bytes.
|
|
package sha3 // import "golang.org/x/crypto/sha3"
|