tzhash/tz/hash.go

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// Copyright 2018 (c) NSPCC
//
// Package tz implements general Tillich-Zemo
package tz
import (
"errors"
"hash"
"golang.org/x/sys/cpu"
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)
type Implementation int
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const (
hashSize = 64
hashBlockSize = 128
_ Implementation = iota
AVX
AVX2
AVX2Inline
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PureGo
AVXInline
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)
var (
hasAVX = cpu.X86.HasAVX
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// Having AVX2 does not guarantee
// that AVX is also present.
hasAVX2 = cpu.X86.HasAVX2 && hasAVX
)
func (impl Implementation) String() string {
switch impl {
case AVX:
return "AVX"
case AVXInline:
return "AVXInline"
case AVX2:
return "AVX2"
case AVX2Inline:
return "AVX2Inline"
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case PureGo:
return "PureGo"
default:
return "UNKNOWN"
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}
}
func NewWith(impl Implementation) hash.Hash {
switch impl {
case AVX:
return newAVX()
case AVXInline:
return newAVXInline()
case AVX2:
return newAVX2()
case AVX2Inline:
return newAVX2Inline()
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case PureGo:
return newPure()
default:
return New()
}
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}
// New returns a new hash.Hash computing the Tillich-Zémor checksum.
func New() hash.Hash {
if hasAVX2 {
return newAVX2Inline()
} else if hasAVX {
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return newAVXInline()
} else {
return newPure()
}
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}
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// Sum returns Tillich-Zémor checksum of data.
func Sum(data []byte) [hashSize]byte {
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if hasAVX2 {
d := newAVX2Inline()
_, _ = d.Write(data) // no errors
return d.checkSum()
} else if hasAVX {
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d := newAVXInline()
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_, _ = d.Write(data) // no errors
return d.checkSum()
} else {
d := newPure()
_, _ = d.Write(data) // no errors
return d.checkSum()
}
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}
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// Concat performs combining of hashes based on homomorphic property.
func Concat(hs [][]byte) ([]byte, error) {
var b, c sl2
b = id
for i := range hs {
if err := c.UnmarshalBinary(hs[i]); err != nil {
return nil, err
}
b.Mul(&b, &c)
}
return b.MarshalBinary()
}
// Validate checks if hashes in hs combined are equal to h.
func Validate(h []byte, hs [][]byte) (bool, error) {
var (
b []byte
got, expected [hashSize]byte
err error
)
if len(h) != hashSize {
return false, errors.New("invalid hash")
} else if len(hs) == 0 {
return false, errors.New("empty slice")
}
copy(expected[:], h)
b, err = Concat(hs)
if err != nil {
return false, errors.New("cant concatenate hashes")
}
copy(got[:], b)
return expected == got, nil
}
// SubtractR returns hash a, such that Concat(a, b) == c
// This is possible, because Tillich-Zemor hash is actually a matrix
// which can be inversed.
func SubtractR(c, b []byte) (a []byte, err error) {
var p1, p2, r sl2
if err = r.UnmarshalBinary(c); err != nil {
return nil, err
}
if err = p2.UnmarshalBinary(b); err != nil {
return nil, err
}
p1 = *Inv(&p2)
p1.Mul(&r, &p1)
return p1.MarshalBinary()
}
// SubtractL returns hash b, such that Concat(a, b) == c
// This is possible, because Tillich-Zemor hash is actually a matrix
// which can be inversed.
func SubtractL(c, a []byte) (b []byte, err error) {
var p1, p2, r sl2
if err = r.UnmarshalBinary(c); err != nil {
return nil, err
}
if err = p1.UnmarshalBinary(a); err != nil {
return nil, err
}
p2 = *Inv(&p1)
p2.Mul(&p2, &r)
return p2.MarshalBinary()
}