S-DES

s-des.js

var BitArray = require('node-bitarray');

var text = BitArray.fromBinary('10110110').toJSON().reverse();
var key = BitArray.fromBinary('1111010110').toJSON().reverse();
var extendTransposition = [1, 4, 3, 4, 2, 1, 3, 2];
var transposition = [3, 4, 2, 1];
var s1 = [[0, 1, 2, 1], [2, 3, 0, 3], [2, 1, 2, 1], [3, 0, 3, 0]];
var s2 = [[0, 2, 0 ,1], [0, 1, 3, 2], [3, 2, 3, 1], [0, 2, 3, 1]];

var p_pryamoi = [3, 5, 2, 7, 4, 10, 1, 9, 8, 6]
var p_sjatie = [6, 3, 7, 4, 8, 5, 10, 9]
var nach = [2, 6, 3, 1, 4, 8, 5, 7]
var con = [4, 1, 3, 5, 7, 2, 8, 6]


function permutation(input, scheme) {
	return input.map(function(item, index, arr) {
		return arr[scheme[index]-1];
	});
}

function shift(input, shiftValue) {
	return input.map(function(item, index, arr) {
		return arr[(index + shiftValue) % arr.length];
	});	
}

function size(input, scheme) {
	return scheme.map(function (item, index) {
		return input[item-1];
	})
}

function getValueFromBlock(input, block) {
	var copiedInput = input.slice();

	console.log(input);

	var valY = new BitArray(copiedInput.splice(1, 2).reverse()).toNumber();
	var valX = new BitArray(copiedInput.reverse()).toNumber();

	console.log('valY: ', valY);
	console.log('valX: ', valX);

	
	var result =  block[valX][valY];

	return BitArray.factory(result, 2).reverse();
}

function initialize(key) {
	var workingKey = key.slice();

	console.log(workingKey);
	console.log('extendedTransposition: ', extendTransposition);
	console.log('transposition: ', transposition);

	var transpositionKey =  permutation(key, p_pryamoi);
	var L0 = transpositionKey.slice(0, 5);
	var R0 = transpositionKey.slice(5);

	console.log('L0: ', L0);
	console.log('R0: ', R0);

	var shiftL0_1 = shift(L0, 1);
	var shiftR0_1 = shift(R0, 1);

	console.log('shift_L0_1: ', shiftL0_1);
	console.log('shift_R0_1: ', shiftR0_1);

	var key1 = size(shiftL0_1.concat(shiftR0_1), p_sjatie);
	console.log('Key1: ', key1);

	var shiftL0_2 = shift(shiftL0_1, 2);
	var shiftR0_2 = shift(shiftR0_1, 2);

	console.log('shift_L0_2: ', shiftL0_1);
	console.log('shift_R0_2: ', shiftR0_1);

	var key2 = size(shiftL0_2.concat(shiftR0_2), p_sjatie);
	console.log('Key2: ', key2);

	return { key1: key1, key2: key2};
}


function round(input, input1, key) {
	var extendInput = size(input, extendTransposition);

	console.log('extendInput: ', extendInput);
	console.log('Round1 key: ', key);

	var xorResult = BitArray.xor(extendInput, key, BitArray.octet([]));
	console.log('XOR result: ', xorResult);

	var L = xorResult.slice(0, 4);
	var R = xorResult.slice(4);

	var s1_val = getValueFromBlock(L, s1);
	var s2_val = getValueFromBlock(R, s2);

	console.log('s1_val: ', s1_val);
	console.log('s2_val: ', s2_val);

	var block_val = s1_val.concat(s2_val);
	var valueWithTransposition = permutation(block_val, transposition);

	console.log('valueWithTransposition: ', valueWithTransposition);

	console.log('Input: ', input);

	var output = BitArray.xor(valueWithTransposition, input1, BitArray.factory(0, 4));

	console.log('Output: ', output);

	return output;

}



console.log('--------------CODING--------------');

var keys = initialize(key);
var textWithPermutation = permutation(text, nach);

var L0 = textWithPermutation.slice(0, 4);
var R0 = textWithPermutation.slice(4);

var L1 = R0.slice();
var R1 = round(L1, L0, keys.key1);

var R2 = R1.slice();
var L2 = round(R2, L1, keys.key2);

var LR2 = L2.concat(R2);
var ciphertext = permutation(LR2, con);

console.log('Ciphertext: ', ciphertext);


console.log('-------------DECODING-------------');
var textWithPermutation = permutation(ciphertext, nach);

var L2 = textWithPermutation.slice(0, 4);
var R2 = textWithPermutation.slice(4);

var R1 = round(R2, L2, keys.key2);
var L1 = R2.slice();

var L0 = round(R1, L1, keys.key1);
var R0 = R1.slice();

var LR0 = L0.concat(R0);
var decodedtext = permutation(LR0, con);


console.log('Decoded text: ', decodedtext);