var Buffer = require('safe-buffer').Buffer
|
var ZEROES = Buffer.alloc(16, 0)
|
|
function toArray (buf) {
|
return [
|
buf.readUInt32BE(0),
|
buf.readUInt32BE(4),
|
buf.readUInt32BE(8),
|
buf.readUInt32BE(12)
|
]
|
}
|
|
function fromArray (out) {
|
var buf = Buffer.allocUnsafe(16)
|
buf.writeUInt32BE(out[0] >>> 0, 0)
|
buf.writeUInt32BE(out[1] >>> 0, 4)
|
buf.writeUInt32BE(out[2] >>> 0, 8)
|
buf.writeUInt32BE(out[3] >>> 0, 12)
|
return buf
|
}
|
|
function GHASH (key) {
|
this.h = key
|
this.state = Buffer.alloc(16, 0)
|
this.cache = Buffer.allocUnsafe(0)
|
}
|
|
// from http://bitwiseshiftleft.github.io/sjcl/doc/symbols/src/core_gcm.js.html
|
// by Juho Vähä-Herttua
|
GHASH.prototype.ghash = function (block) {
|
var i = -1
|
while (++i < block.length) {
|
this.state[i] ^= block[i]
|
}
|
this._multiply()
|
}
|
|
GHASH.prototype._multiply = function () {
|
var Vi = toArray(this.h)
|
var Zi = [0, 0, 0, 0]
|
var j, xi, lsbVi
|
var i = -1
|
while (++i < 128) {
|
xi = (this.state[~~(i / 8)] & (1 << (7 - (i % 8)))) !== 0
|
if (xi) {
|
// Z_i+1 = Z_i ^ V_i
|
Zi[0] ^= Vi[0]
|
Zi[1] ^= Vi[1]
|
Zi[2] ^= Vi[2]
|
Zi[3] ^= Vi[3]
|
}
|
|
// Store the value of LSB(V_i)
|
lsbVi = (Vi[3] & 1) !== 0
|
|
// V_i+1 = V_i >> 1
|
for (j = 3; j > 0; j--) {
|
Vi[j] = (Vi[j] >>> 1) | ((Vi[j - 1] & 1) << 31)
|
}
|
Vi[0] = Vi[0] >>> 1
|
|
// If LSB(V_i) is 1, V_i+1 = (V_i >> 1) ^ R
|
if (lsbVi) {
|
Vi[0] = Vi[0] ^ (0xe1 << 24)
|
}
|
}
|
this.state = fromArray(Zi)
|
}
|
|
GHASH.prototype.update = function (buf) {
|
this.cache = Buffer.concat([this.cache, buf])
|
var chunk
|
while (this.cache.length >= 16) {
|
chunk = this.cache.slice(0, 16)
|
this.cache = this.cache.slice(16)
|
this.ghash(chunk)
|
}
|
}
|
|
GHASH.prototype.final = function (abl, bl) {
|
if (this.cache.length) {
|
this.ghash(Buffer.concat([this.cache, ZEROES], 16))
|
}
|
|
this.ghash(fromArray([0, abl, 0, bl]))
|
return this.state
|
}
|
|
module.exports = GHASH
|
