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@@ -1,237 +1,193 @@
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-// Copyright 2013 The Go Authors. All rights reserved.
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-//
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-// Redistribution and use in source and binary forms, with or without
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-// modification, are permitted provided that the following conditions are
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-// met:
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-//
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-// * Redistributions of source code must retain the above copyright
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-// notice, this list of conditions and the following disclaimer.
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-// * Redistributions in binary form must reproduce the above
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-// copyright notice, this list of conditions and the following disclaimer
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-// in the documentation and/or other materials provided with the
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-// distribution.
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-// * Neither the name of Google Inc. nor the names of its
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-// contributors may be used to endorse or promote products derived from
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-// this software without specific prior written permission.
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-//
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-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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-
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-// Package sha3 implements the SHA3 hash algorithm (formerly called Keccak) chosen by NIST in 2012.
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-// This file provides a SHA3 implementation which implements the standard hash.Hash interface.
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-// Writing input data, including padding, and reading output data are computed in this file.
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-// Note that the current implementation can compute the hash of an integral number of bytes only.
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-// This is a consequence of the hash interface in which a buffer of bytes is passed in.
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-// The internals of the Keccak-f function are computed in keccakf.go.
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-// For the detailed specification, refer to the Keccak web site (http://keccak.noekeon.org/).
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+// Copyright 2014 The Go Authors. All rights reserved.
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+// Use of this source code is governed by a BSD-style
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+// license that can be found in the LICENSE file.
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+
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package sha3
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-import (
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- "encoding/binary"
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- "hash"
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+// spongeDirection indicates the direction bytes are flowing through the sponge.
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+type spongeDirection int
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+
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+const (
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+ // spongeAbsorbing indicates that the sponge is absorbing input.
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+ spongeAbsorbing spongeDirection = iota
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+ // spongeSqueezing indicates that the sponge is being squeezed.
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+ spongeSqueezing
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)
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-// laneSize is the size in bytes of each "lane" of the internal state of SHA3 (5 * 5 * 8).
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-// Note that changing this size would requires using a type other than uint64 to store each lane.
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-const laneSize = 8
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-
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-// sliceSize represents the dimensions of the internal state, a square matrix of
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-// sliceSize ** 2 lanes. This is the size of both the "rows" and "columns" dimensions in the
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-// terminology of the SHA3 specification.
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-const sliceSize = 5
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-
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-// numLanes represents the total number of lanes in the state.
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-const numLanes = sliceSize * sliceSize
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-
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-// stateSize is the size in bytes of the internal state of SHA3 (5 * 5 * WSize).
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-const stateSize = laneSize * numLanes
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-
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-// digest represents the partial evaluation of a checksum.
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-// Note that capacity, and not outputSize, is the critical security parameter, as SHA3 can output
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-// an arbitrary number of bytes for any given capacity. The Keccak proposal recommends that
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-// capacity = 2*outputSize to ensure that finding a collision of size outputSize requires
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-// O(2^{outputSize/2}) computations (the birthday lower bound). Future standards may modify the
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-// capacity/outputSize ratio to allow for more output with lower cryptographic security.
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-type digest struct {
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- a [numLanes]uint64 // main state of the hash
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- outputSize int // desired output size in bytes
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- capacity int // number of bytes to leave untouched during squeeze/absorb
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- absorbed int // number of bytes absorbed thus far
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-}
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+const (
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+ // maxRate is the maximum size of the internal buffer. SHAKE-256
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+ // currently needs the largest buffer.
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+ maxRate = 168
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+)
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-// minInt returns the lesser of two integer arguments, to simplify the absorption routine.
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-func minInt(v1, v2 int) int {
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- if v1 <= v2 {
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- return v1
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- }
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- return v2
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+type state struct {
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+ // Generic sponge components.
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+ a [25]uint64 // main state of the hash
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+ buf []byte // points into storage
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+ rate int // the number of bytes of state to use
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+
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+ // dsbyte contains the "domain separation" bits and the first bit of
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+ // the padding. Sections 6.1 and 6.2 of [1] separate the outputs of the
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+ // SHA-3 and SHAKE functions by appending bitstrings to the message.
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+ // Using a little-endian bit-ordering convention, these are "01" for SHA-3
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+ // and "1111" for SHAKE, or 00000010b and 00001111b, respectively. Then the
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+ // padding rule from section 5.1 is applied to pad the message to a multiple
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+ // of the rate, which involves adding a "1" bit, zero or more "0" bits, and
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+ // a final "1" bit. We merge the first "1" bit from the padding into dsbyte,
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+ // giving 00000110b (0x06) and 00011111b (0x1f).
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+ // [1] http://csrc.nist.gov/publications/drafts/fips-202/fips_202_draft.pdf
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+ // "Draft FIPS 202: SHA-3 Standard: Permutation-Based Hash and
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+ // Extendable-Output Functions (May 2014)"
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+ dsbyte byte
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+ storage [maxRate]byte
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+
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+ // Specific to SHA-3 and SHAKE.
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+ fixedOutput bool // whether this is a fixed-ouput-length instance
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+ outputLen int // the default output size in bytes
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+ state spongeDirection // whether the sponge is absorbing or squeezing
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}
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-// rate returns the number of bytes of the internal state which can be absorbed or squeezed
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-// in between calls to the permutation function.
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-func (d *digest) rate() int {
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- return stateSize - d.capacity
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-}
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+// BlockSize returns the rate of sponge underlying this hash function.
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+func (d *state) BlockSize() int { return d.rate }
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+
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+// Size returns the output size of the hash function in bytes.
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+func (d *state) Size() int { return d.outputLen }
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-// Reset clears the internal state by zeroing bytes in the state buffer.
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-// This can be skipped for a newly-created hash state; the default zero-allocated state is correct.
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-func (d *digest) Reset() {
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- d.absorbed = 0
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+// Reset clears the internal state by zeroing the sponge state and
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+// the byte buffer, and setting Sponge.state to absorbing.
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+func (d *state) Reset() {
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+ // Zero the permutation's state.
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for i := range d.a {
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d.a[i] = 0
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}
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+ d.state = spongeAbsorbing
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+ d.buf = d.storage[:0]
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}
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-// BlockSize, required by the hash.Hash interface, does not have a standard intepretation
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-// for a sponge-based construction like SHA3. We return the data rate: the number of bytes which
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-// can be absorbed per invocation of the permutation function. For Merkle-Damgård based hashes
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-// (ie SHA1, SHA2, MD5) the output size of the internal compression function is returned.
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-// We consider this to be roughly equivalent because it represents the number of bytes of output
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-// produced per cryptographic operation.
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-func (d *digest) BlockSize() int { return d.rate() }
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+func (d *state) clone() *state {
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+ ret := *d
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+ if ret.state == spongeAbsorbing {
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+ ret.buf = ret.storage[:len(ret.buf)]
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+ } else {
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+ ret.buf = ret.storage[d.rate-cap(d.buf) : d.rate]
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+ }
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-// Size returns the output size of the hash function in bytes.
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-func (d *digest) Size() int {
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- return d.outputSize
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+ return &ret
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}
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-// unalignedAbsorb is a helper function for Write, which absorbs data that isn't aligned with an
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-// 8-byte lane. This requires shifting the individual bytes into position in a uint64.
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-func (d *digest) unalignedAbsorb(p []byte) {
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- var t uint64
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- for i := len(p) - 1; i >= 0; i-- {
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- t <<= 8
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- t |= uint64(p[i])
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+// permute applies the KeccakF-1600 permutation. It handles
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+// any input-output buffering.
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+func (d *state) permute() {
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+ switch d.state {
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+ case spongeAbsorbing:
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+ // If we're absorbing, we need to xor the input into the state
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+ // before applying the permutation.
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+ xorIn(d, d.buf)
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+ d.buf = d.storage[:0]
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+ keccakF1600(&d.a)
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+ case spongeSqueezing:
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+ // If we're squeezing, we need to apply the permutatin before
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+ // copying more output.
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+ keccakF1600(&d.a)
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+ d.buf = d.storage[:d.rate]
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+ copyOut(d, d.buf)
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}
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- offset := (d.absorbed) % d.rate()
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- t <<= 8 * uint(offset%laneSize)
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- d.a[offset/laneSize] ^= t
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- d.absorbed += len(p)
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}
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-// Write "absorbs" bytes into the state of the SHA3 hash, updating as needed when the sponge
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-// "fills up" with rate() bytes. Since lanes are stored internally as type uint64, this requires
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-// converting the incoming bytes into uint64s using a little endian interpretation. This
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-// implementation is optimized for large, aligned writes of multiples of 8 bytes (laneSize).
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-// Non-aligned or uneven numbers of bytes require shifting and are slower.
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-func (d *digest) Write(p []byte) (int, error) {
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- // An initial offset is needed if the we aren't absorbing to the first lane initially.
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- offset := d.absorbed % d.rate()
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- toWrite := len(p)
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-
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- // The first lane may need to absorb unaligned and/or incomplete data.
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- if (offset%laneSize != 0 || len(p) < 8) && len(p) > 0 {
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- toAbsorb := minInt(laneSize-(offset%laneSize), len(p))
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- d.unalignedAbsorb(p[:toAbsorb])
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- p = p[toAbsorb:]
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- offset = (d.absorbed) % d.rate()
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-
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- // For every rate() bytes absorbed, the state must be permuted via the F Function.
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- if (d.absorbed)%d.rate() == 0 {
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- keccakF1600(&d.a)
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- }
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+// pads appends the domain separation bits in dsbyte, applies
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+// the multi-bitrate 10..1 padding rule, and permutes the state.
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+func (d *state) padAndPermute(dsbyte byte) {
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+ if d.buf == nil {
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+ d.buf = d.storage[:0]
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}
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+ // Pad with this instance's domain-separator bits. We know that there's
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+ // at least one byte of space in d.buf because, if it were full,
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+ // permute would have been called to empty it. dsbyte also contains the
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+ // first one bit for the padding. See the comment in the state struct.
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+ d.buf = append(d.buf, dsbyte)
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+ zerosStart := len(d.buf)
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+ d.buf = d.storage[:d.rate]
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+ for i := zerosStart; i < d.rate; i++ {
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+ d.buf[i] = 0
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+ }
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+ // This adds the final one bit for the padding. Because of the way that
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+ // bits are numbered from the LSB upwards, the final bit is the MSB of
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+ // the last byte.
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+ d.buf[d.rate-1] ^= 0x80
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+ // Apply the permutation
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+ d.permute()
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+ d.state = spongeSqueezing
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+ d.buf = d.storage[:d.rate]
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+ copyOut(d, d.buf)
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+}
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- // This loop should absorb the bulk of the data into full, aligned lanes.
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- // It will call the update function as necessary.
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- for len(p) > 7 {
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- firstLane := offset / laneSize
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- lastLane := minInt(d.rate()/laneSize, firstLane+len(p)/laneSize)
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+// Write absorbs more data into the hash's state. It produces an error
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+// if more data is written to the ShakeHash after writing
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+func (d *state) Write(p []byte) (written int, err error) {
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+ if d.state != spongeAbsorbing {
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+ panic("sha3: write to sponge after read")
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+ }
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+ if d.buf == nil {
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+ d.buf = d.storage[:0]
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+ }
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+ written = len(p)
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- // This inner loop absorbs input bytes into the state in groups of 8, converted to uint64s.
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- for lane := firstLane; lane < lastLane; lane++ {
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- d.a[lane] ^= binary.LittleEndian.Uint64(p[:laneSize])
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- p = p[laneSize:]
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- }
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- d.absorbed += (lastLane - firstLane) * laneSize
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- // For every rate() bytes absorbed, the state must be permuted via the F Function.
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- if (d.absorbed)%d.rate() == 0 {
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+ for len(p) > 0 {
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+ if len(d.buf) == 0 && len(p) >= d.rate {
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+ // The fast path; absorb a full "rate" bytes of input and apply the permutation.
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+ xorIn(d, p[:d.rate])
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+ p = p[d.rate:]
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keccakF1600(&d.a)
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+ } else {
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+ // The slow path; buffer the input until we can fill the sponge, and then xor it in.
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+ todo := d.rate - len(d.buf)
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+ if todo > len(p) {
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+ todo = len(p)
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+ }
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+ d.buf = append(d.buf, p[:todo]...)
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+ p = p[todo:]
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+
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+ // If the sponge is full, apply the permutation.
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+ if len(d.buf) == d.rate {
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+ d.permute()
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+ }
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}
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-
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- offset = 0
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- }
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-
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- // If there are insufficient bytes to fill the final lane, an unaligned absorption.
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- // This should always start at a correct lane boundary though, or else it would be caught
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- // by the uneven opening lane case above.
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- if len(p) > 0 {
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- d.unalignedAbsorb(p)
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}
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- return toWrite, nil
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-}
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-
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-// pad computes the SHA3 padding scheme based on the number of bytes absorbed.
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-// The padding is a 1 bit, followed by an arbitrary number of 0s and then a final 1 bit, such that
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-// the input bits plus padding bits are a multiple of rate(). Adding the padding simply requires
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-// xoring an opening and closing bit into the appropriate lanes.
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-func (d *digest) pad() {
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- offset := d.absorbed % d.rate()
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- // The opening pad bit must be shifted into position based on the number of bytes absorbed
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- padOpenLane := offset / laneSize
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- d.a[padOpenLane] ^= 0x0000000000000001 << uint(8*(offset%laneSize))
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- // The closing padding bit is always in the last position
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- padCloseLane := (d.rate() / laneSize) - 1
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- d.a[padCloseLane] ^= 0x8000000000000000
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+ return
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}
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-// finalize prepares the hash to output data by padding and one final permutation of the state.
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-func (d *digest) finalize() {
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- d.pad()
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- keccakF1600(&d.a)
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-}
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-
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-// squeeze outputs an arbitrary number of bytes from the hash state.
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-// Squeezing can require multiple calls to the F function (one per rate() bytes squeezed),
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-// although this is not the case for standard SHA3 parameters. This implementation only supports
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-// squeezing a single time, subsequent squeezes may lose alignment. Future implementations
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-// may wish to support multiple squeeze calls, for example to support use as a PRNG.
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-func (d *digest) squeeze(in []byte, toSqueeze int) []byte {
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- // Because we read in blocks of laneSize, we need enough room to read
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- // an integral number of lanes
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- needed := toSqueeze + (laneSize-toSqueeze%laneSize)%laneSize
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- if cap(in)-len(in) < needed {
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- newIn := make([]byte, len(in), len(in)+needed)
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- copy(newIn, in)
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- in = newIn
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+// Read squeezes an arbitrary number of bytes from the sponge.
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+func (d *state) Read(out []byte) (n int, err error) {
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+ // If we're still absorbing, pad and apply the permutation.
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+ if d.state == spongeAbsorbing {
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+ d.padAndPermute(d.dsbyte)
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}
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- out := in[len(in) : len(in)+needed]
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+ n = len(out)
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+
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+ // Now, do the squeezing.
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for len(out) > 0 {
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- for i := 0; i < d.rate() && len(out) > 0; i += laneSize {
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- binary.LittleEndian.PutUint64(out[:], d.a[i/laneSize])
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- out = out[laneSize:]
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- }
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- if len(out) > 0 {
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- keccakF1600(&d.a)
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+ n := copy(out, d.buf)
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+ d.buf = d.buf[n:]
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+ out = out[n:]
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+
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+ // Apply the permutation if we've squeezed the sponge dry.
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+ if len(d.buf) == 0 {
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+ d.permute()
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}
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}
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- return in[:len(in)+toSqueeze] // Re-slice in case we wrote extra data.
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-}
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|
-// Sum applies padding to the hash state and then squeezes out the desired nubmer of output bytes.
|
|
|
-func (d *digest) Sum(in []byte) []byte {
|
|
|
- // Make a copy of the original hash so that caller can keep writing and summing.
|
|
|
- dup := *d
|
|
|
- dup.finalize()
|
|
|
- return dup.squeeze(in, dup.outputSize)
|
|
|
+ return
|
|
|
}
|
|
|
|
|
|
-// The NewKeccakX constructors enable initializing a hash in any of the four recommend sizes
|
|
|
-// from the Keccak specification, all of which set capacity=2*outputSize. Note that the final
|
|
|
-// NIST standard for SHA3 may specify different input/output lengths.
|
|
|
-// The output size is indicated in bits but converted into bytes internally.
|
|
|
-func NewKeccak224() hash.Hash { return &digest{outputSize: 224 / 8, capacity: 2 * 224 / 8} }
|
|
|
-func NewKeccak256() hash.Hash { return &digest{outputSize: 256 / 8, capacity: 2 * 256 / 8} }
|
|
|
-func NewKeccak384() hash.Hash { return &digest{outputSize: 384 / 8, capacity: 2 * 384 / 8} }
|
|
|
-func NewKeccak512() hash.Hash { return &digest{outputSize: 512 / 8, capacity: 2 * 512 / 8} }
|
|
|
+// Sum applies padding to the hash state and then squeezes out the desired
|
|
|
+// number of output bytes.
|
|
|
+func (d *state) Sum(in []byte) []byte {
|
|
|
+ // Make a copy of the original hash so that caller can keep writing
|
|
|
+ // and summing.
|
|
|
+ dup := d.clone()
|
|
|
+ hash := make([]byte, dup.outputLen)
|
|
|
+ dup.Read(hash)
|
|
|
+ return append(in, hash...)
|
|
|
+}
|