'use strict';
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var assert = require('minimalistic-assert');
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var inherits = require('inherits');
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var utils = require('./utils');
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var Cipher = require('./cipher');
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function DESState() {
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this.tmp = new Array(2);
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this.keys = null;
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}
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function DES(options) {
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Cipher.call(this, options);
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var state = new DESState();
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this._desState = state;
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this.deriveKeys(state, options.key);
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}
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inherits(DES, Cipher);
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module.exports = DES;
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DES.create = function create(options) {
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return new DES(options);
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};
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var shiftTable = [
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1, 1, 2, 2, 2, 2, 2, 2,
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1, 2, 2, 2, 2, 2, 2, 1
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];
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DES.prototype.deriveKeys = function deriveKeys(state, key) {
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state.keys = new Array(16 * 2);
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assert.equal(key.length, this.blockSize, 'Invalid key length');
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var kL = utils.readUInt32BE(key, 0);
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var kR = utils.readUInt32BE(key, 4);
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utils.pc1(kL, kR, state.tmp, 0);
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kL = state.tmp[0];
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kR = state.tmp[1];
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for (var i = 0; i < state.keys.length; i += 2) {
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var shift = shiftTable[i >>> 1];
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kL = utils.r28shl(kL, shift);
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kR = utils.r28shl(kR, shift);
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utils.pc2(kL, kR, state.keys, i);
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}
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};
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DES.prototype._update = function _update(inp, inOff, out, outOff) {
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var state = this._desState;
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var l = utils.readUInt32BE(inp, inOff);
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var r = utils.readUInt32BE(inp, inOff + 4);
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// Initial Permutation
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utils.ip(l, r, state.tmp, 0);
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l = state.tmp[0];
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r = state.tmp[1];
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if (this.type === 'encrypt')
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this._encrypt(state, l, r, state.tmp, 0);
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else
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this._decrypt(state, l, r, state.tmp, 0);
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l = state.tmp[0];
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r = state.tmp[1];
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utils.writeUInt32BE(out, l, outOff);
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utils.writeUInt32BE(out, r, outOff + 4);
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};
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DES.prototype._pad = function _pad(buffer, off) {
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var value = buffer.length - off;
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for (var i = off; i < buffer.length; i++)
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buffer[i] = value;
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return true;
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};
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DES.prototype._unpad = function _unpad(buffer) {
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var pad = buffer[buffer.length - 1];
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for (var i = buffer.length - pad; i < buffer.length; i++)
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assert.equal(buffer[i], pad);
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return buffer.slice(0, buffer.length - pad);
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};
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DES.prototype._encrypt = function _encrypt(state, lStart, rStart, out, off) {
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var l = lStart;
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var r = rStart;
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// Apply f() x16 times
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for (var i = 0; i < state.keys.length; i += 2) {
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var keyL = state.keys[i];
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var keyR = state.keys[i + 1];
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// f(r, k)
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utils.expand(r, state.tmp, 0);
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keyL ^= state.tmp[0];
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keyR ^= state.tmp[1];
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var s = utils.substitute(keyL, keyR);
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var f = utils.permute(s);
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var t = r;
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r = (l ^ f) >>> 0;
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l = t;
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}
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// Reverse Initial Permutation
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utils.rip(r, l, out, off);
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};
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DES.prototype._decrypt = function _decrypt(state, lStart, rStart, out, off) {
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var l = rStart;
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var r = lStart;
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// Apply f() x16 times
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for (var i = state.keys.length - 2; i >= 0; i -= 2) {
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var keyL = state.keys[i];
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var keyR = state.keys[i + 1];
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// f(r, k)
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utils.expand(l, state.tmp, 0);
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keyL ^= state.tmp[0];
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keyR ^= state.tmp[1];
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var s = utils.substitute(keyL, keyR);
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var f = utils.permute(s);
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var t = l;
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l = (r ^ f) >>> 0;
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r = t;
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}
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// Reverse Initial Permutation
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utils.rip(l, r, out, off);
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};
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