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Diffstat (limited to 'vendor/golang.org/x/crypto/sha3/shake.go')
-rw-r--r-- | vendor/golang.org/x/crypto/sha3/shake.go | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/sha3/shake.go b/vendor/golang.org/x/crypto/sha3/shake.go new file mode 100644 index 0000000..d7be295 --- /dev/null +++ b/vendor/golang.org/x/crypto/sha3/shake.go @@ -0,0 +1,173 @@ +// 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 + +// This file defines the ShakeHash interface, and provides +// functions for creating SHAKE and cSHAKE instances, as well as utility +// functions for hashing bytes to arbitrary-length output. +// +// +// SHAKE implementation is based on FIPS PUB 202 [1] +// cSHAKE implementations is based on NIST SP 800-185 [2] +// +// [1] https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf +// [2] https://doi.org/10.6028/NIST.SP.800-185 + +import ( + "encoding/binary" + "io" +) + +// ShakeHash defines the interface to hash functions that +// support arbitrary-length output. +type ShakeHash interface { + // Write absorbs more data into the hash's state. It panics if input is + // written to it after output has been read from it. + io.Writer + + // Read reads more output from the hash; reading affects the hash's + // state. (ShakeHash.Read is thus very different from Hash.Sum) + // It never returns an error. + io.Reader + + // Clone returns a copy of the ShakeHash in its current state. + Clone() ShakeHash + + // Reset resets the ShakeHash to its initial state. + Reset() +} + +// cSHAKE specific context +type cshakeState struct { + *state // SHA-3 state context and Read/Write operations + + // initBlock is the cSHAKE specific initialization set of bytes. It is initialized + // by newCShake function and stores concatenation of N followed by S, encoded + // by the method specified in 3.3 of [1]. + // It is stored here in order for Reset() to be able to put context into + // initial state. + initBlock []byte +} + +// Consts for configuring initial SHA-3 state +const ( + dsbyteShake = 0x1f + dsbyteCShake = 0x04 + rate128 = 168 + rate256 = 136 +) + +func bytepad(input []byte, w int) []byte { + // leftEncode always returns max 9 bytes + buf := make([]byte, 0, 9+len(input)+w) + buf = append(buf, leftEncode(uint64(w))...) + buf = append(buf, input...) + padlen := w - (len(buf) % w) + return append(buf, make([]byte, padlen)...) +} + +func leftEncode(value uint64) []byte { + var b [9]byte + binary.BigEndian.PutUint64(b[1:], value) + // Trim all but last leading zero bytes + i := byte(1) + for i < 8 && b[i] == 0 { + i++ + } + // Prepend number of encoded bytes + b[i-1] = 9 - i + return b[i-1:] +} + +func newCShake(N, S []byte, rate int, dsbyte byte) ShakeHash { + c := cshakeState{state: &state{rate: rate, dsbyte: dsbyte}} + + // leftEncode returns max 9 bytes + c.initBlock = make([]byte, 0, 9*2+len(N)+len(S)) + c.initBlock = append(c.initBlock, leftEncode(uint64(len(N)*8))...) + c.initBlock = append(c.initBlock, N...) + c.initBlock = append(c.initBlock, leftEncode(uint64(len(S)*8))...) + c.initBlock = append(c.initBlock, S...) + c.Write(bytepad(c.initBlock, c.rate)) + return &c +} + +// Reset resets the hash to initial state. +func (c *cshakeState) Reset() { + c.state.Reset() + c.Write(bytepad(c.initBlock, c.rate)) +} + +// Clone returns copy of a cSHAKE context within its current state. +func (c *cshakeState) Clone() ShakeHash { + b := make([]byte, len(c.initBlock)) + copy(b, c.initBlock) + return &cshakeState{state: c.clone(), initBlock: b} +} + +// Clone returns copy of SHAKE context within its current state. +func (c *state) Clone() ShakeHash { + return c.clone() +} + +// NewShake128 creates a new SHAKE128 variable-output-length ShakeHash. +// Its generic security strength is 128 bits against all attacks if at +// least 32 bytes of its output are used. +func NewShake128() ShakeHash { + if h := newShake128Asm(); h != nil { + return h + } + return &state{rate: rate128, dsbyte: dsbyteShake} +} + +// NewShake256 creates a new SHAKE256 variable-output-length ShakeHash. +// Its generic security strength is 256 bits against all attacks if +// at least 64 bytes of its output are used. +func NewShake256() ShakeHash { + if h := newShake256Asm(); h != nil { + return h + } + return &state{rate: rate256, dsbyte: dsbyteShake} +} + +// NewCShake128 creates a new instance of cSHAKE128 variable-output-length ShakeHash, +// a customizable variant of SHAKE128. +// N is used to define functions based on cSHAKE, it can be empty when plain cSHAKE is +// desired. S is a customization byte string used for domain separation - two cSHAKE +// computations on same input with different S yield unrelated outputs. +// When N and S are both empty, this is equivalent to NewShake128. +func NewCShake128(N, S []byte) ShakeHash { + if len(N) == 0 && len(S) == 0 { + return NewShake128() + } + return newCShake(N, S, rate128, dsbyteCShake) +} + +// NewCShake256 creates a new instance of cSHAKE256 variable-output-length ShakeHash, +// a customizable variant of SHAKE256. +// N is used to define functions based on cSHAKE, it can be empty when plain cSHAKE is +// desired. S is a customization byte string used for domain separation - two cSHAKE +// computations on same input with different S yield unrelated outputs. +// When N and S are both empty, this is equivalent to NewShake256. +func NewCShake256(N, S []byte) ShakeHash { + if len(N) == 0 && len(S) == 0 { + return NewShake256() + } + return newCShake(N, S, rate256, dsbyteCShake) +} + +// ShakeSum128 writes an arbitrary-length digest of data into hash. +func ShakeSum128(hash, data []byte) { + h := NewShake128() + h.Write(data) + h.Read(hash) +} + +// ShakeSum256 writes an arbitrary-length digest of data into hash. +func ShakeSum256(hash, data []byte) { + h := NewShake256() + h.Write(data) + h.Read(hash) +} |