tzhash/tz/digest.go

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package tz
import (
"github.com/TrueCloudLab/tzhash/gf127"
)
const (
// Size is the size of a Tillich-Zémor hash sum in bytes.
Size = 64
hashBlockSize = 128
)
type digest struct {
// Stores matrix cells in the following order:
// [ 0 2 ]
// [ 1 3 ]
// This is done to reuse the same digest between generic
// and AVX2 implementation.
x [4]GF127
}
// New returns a new hash.Hash computing the Tillich-Zémor checksum.
func New() *digest {
d := new(digest)
d.Reset()
return d
}
// Sum returns Tillich-Zémor checksum of data.
func Sum(data []byte) [Size]byte {
d := new(digest)
d.Reset()
_, _ = d.Write(data) // no errors
return d.checkSum()
}
// Sum implements hash.Hash.
func (d *digest) Sum(in []byte) []byte {
// Make a copy of d so that caller can keep writing and summing.
d0 := *d
h := d0.checkSum()
return append(in, h[:]...)
}
func (d *digest) checkSum() (b [Size]byte) {
t := d.x[0].Bytes()
copy(b[:], t[:])
t = d.x[2].Bytes()
copy(b[16:], t[:])
t = d.x[1].Bytes()
copy(b[32:], t[:])
t = d.x[3].Bytes()
copy(b[48:], t[:])
return
}
// Reset implements hash.Hash.
func (d *digest) Reset() {
d.x[0] = GF127{1, 0}
d.x[1] = GF127{0, 0}
d.x[2] = GF127{0, 0}
d.x[3] = GF127{1, 0}
}
// Write implements hash.Hash.
func (d *digest) Write(data []byte) (n int, err error) {
return write(d, data)
}
func writeGeneric(d *digest, data []byte) (n int, err error) {
n = len(data)
tmp := new(GF127)
for _, b := range data {
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x80 != 0, tmp)
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x40 != 0, tmp)
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x20 != 0, tmp)
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x10 != 0, tmp)
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x08 != 0, tmp)
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x04 != 0, tmp)
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x02 != 0, tmp)
mulBitRightGeneric(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x01 != 0, tmp)
}
return
}
// Size implements hash.Hash.
func (d *digest) Size() int {
return Size
}
// BlockSize implements hash.Hash.
func (d *digest) BlockSize() int {
return hashBlockSize
}
func mulBitRightGeneric(c00, c10, c01, c11 *GF127, bit bool, tmp *GF127) {
if bit {
*tmp = *c00
gf127.Mul10(c00, c00)
gf127.Add(c00, c01, c00)
gf127.Mul11(tmp, tmp)
gf127.Add(c01, tmp, c01)
*tmp = *c10
gf127.Mul10(c10, c10)
gf127.Add(c10, c11, c10)
gf127.Mul11(tmp, tmp)
gf127.Add(c11, tmp, c11)
} else {
*tmp = *c00
gf127.Mul10(c00, c00)
gf127.Add(c00, c01, c00)
*c01 = *tmp
*tmp = *c10
gf127.Mul10(c10, c10)
gf127.Add(c10, c11, c10)
*c11 = *tmp
}
}