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core.go
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core.go
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package sphincs
import "encoding/binary"
const (
// nMasks has to be the max of (2*(subtreeHeight+wotsLogL)) and (wotsW-1) and 2*horstLogT
nMasks = 2 * horstLogT
nLevels = totalTreeHeight / subtreeHeight
subtreeHeight = 5
totalTreeHeight = 60
seedBytes = 32
skRandSeedBytes = 32
messageHashSeedBytes = 32
)
// leafaddr ...
type leafaddr struct {
level int
subtree uint64
subleaf int
}
// generateSeed ...
func generateSeed(seed, sk []byte, a *leafaddr) {
var buffer [seedBytes + 8]byte
copy(buffer[0:seedBytes], sk[0:seedBytes])
t := uint64(a.level)
t |= a.subtree << 4
t |= uint64(a.subleaf) << 59
binary.LittleEndian.PutUint64(buffer[seedBytes:], t)
hashVarlen(seed, buffer[:])
}
// lTree ...
func lTree(leaf, wotsPk, masks []byte) {
l := wotsL
for i := 0; i < wotsLogL; i++ {
for j := 0; j < l>>1; j++ {
hashH2nnMask(wotsPk[j*hashSize:], wotsPk[j*2*hashSize:], masks[i*2*hashSize:])
}
switch {
case l&1 != 0:
copy(wotsPk[(l>>1)*hashSize:((l>>1)+1)*hashSize], wotsPk[(l-1)*hashSize:])
l = (l >> 1) + 1
default:
l = l >> 1
}
}
copy(leaf[:hashSize], wotsPk[:])
}
// genLeafWots ...
func genLeafWots(leaf, masks, sk []byte, a *leafaddr) {
var seed [seedBytes]byte
var pk [wotsL * hashSize]byte
generateSeed(seed[:], sk, a)
wotsPkgen(pk[:], seed[:], masks)
lTree(leaf, pk[:], masks)
}
// treehash ...
func treehash(node []byte, height int, sk []byte, leaf *leafaddr, masks []byte) {
a := *leaf
stack := make([]byte, (height+1)*hashSize)
stacklevels := make([]uint, height+1)
var stackoffset, maskoffset uint
lastnode := a.subleaf + (1 << uint(height))
for ; a.subleaf < lastnode; a.subleaf++ {
genLeafWots(stack[stackoffset*hashSize:], masks, sk, &a)
stacklevels[stackoffset] = 0
stackoffset++
for stackoffset > 1 && stacklevels[stackoffset-1] == stacklevels[stackoffset-2] {
maskoffset = 2 * (stacklevels[stackoffset-1] + wotsLogL) * hashSize
hashH2nnMask(stack[(stackoffset-2)*hashSize:], stack[(stackoffset-2)*hashSize:], masks[maskoffset:])
stacklevels[stackoffset-2]++
stackoffset--
}
}
copy(node[0:hashSize], stack[0:hashSize])
}
// validateAuthpath ...
func validateAuthpath(root, leaf *[hashSize]byte, leafidx uint, authpath, masks []byte, height uint) {
var buffer [2 * hashSize]byte
switch {
case leafidx&1 != 0:
copy(buffer[hashSize:hashSize*2], leaf[0:hashSize])
copy(buffer[0:hashSize], authpath[0:hashSize])
default:
copy(buffer[0:hashSize], leaf[0:hashSize])
copy(buffer[hashSize:hashSize*2], authpath[0:hashSize])
}
authpath = authpath[hashSize:]
for i := uint(0); i < height-1; i++ {
leafidx >>= 1
switch {
case leafidx&1 != 0:
hashH2nnMask(buffer[hashSize:], buffer[:], masks[2*(wotsLogL+i)*hashSize:])
copy(buffer[0:hashSize], authpath[0:hashSize])
default:
hashH2nnMask(buffer[:], buffer[:], masks[2*(wotsLogL+i)*hashSize:])
copy(buffer[hashSize:hashSize*2], authpath[0:hashSize])
}
authpath = authpath[hashSize:]
}
hashH2nnMask(root[:], buffer[:], masks[2*(wotsLogL+height-1)*hashSize:])
}
// computeAuthpathWots ...
func computeAuthpathWots(root *[hashSize]byte, authpath []byte, a *leafaddr, sk, masks []byte, height uint) {
ta := *a
var tree [2 * (1 << subtreeHeight) * hashSize]byte
var seed [(1 << subtreeHeight) * seedBytes]byte
var pk [(1 << subtreeHeight) * wotsL * hashSize]byte
for ta.subleaf = 0; ta.subleaf < 1<<subtreeHeight; ta.subleaf++ {
generateSeed(seed[ta.subleaf*seedBytes:], sk, &ta)
}
for ta.subleaf = 0; ta.subleaf < 1<<subtreeHeight; ta.subleaf++ {
wotsPkgen(pk[ta.subleaf*wotsL*hashSize:], seed[ta.subleaf*seedBytes:], masks)
}
for ta.subleaf = 0; ta.subleaf < 1<<subtreeHeight; ta.subleaf++ {
lTree(tree[(1<<subtreeHeight)*hashSize+ta.subleaf*hashSize:], pk[ta.subleaf*wotsL*hashSize:], masks)
}
level := 0
for i := 1 << subtreeHeight; i > 0; i >>= 1 {
for j := 0; j < i; j += 2 {
hashH2nnMask(tree[(i>>1)*hashSize+(j>>1)*hashSize:],
tree[i*hashSize+j*hashSize:], masks[2*(wotsLogL+level)*hashSize:])
}
level++
}
idx := a.subleaf
for i := uint(0); i < height; i++ {
dst := authpath[i*hashSize : (i+1)*hashSize]
src := tree[((1<<subtreeHeight)>>i)*hashSize+((idx>>i)^1)*hashSize:]
copy(dst[:], src[:])
}
copy(root[:], tree[hashSize:])
}
// multiSliceAppend ...
func multiSliceAppend(in ...[]byte) []byte {
var out []byte
for _, t := range in {
out = append(out, t...)
}
return out
}