salsa20.js

/*@license taken from https://gist.github.com/dchest/4582374 */

var Salsa20 = (function () {

    function Salsa20(key, nonce) {
        // Constants.
        this.rounds = 20; // number of Salsa rounds
        this.sigmaWords = [0x61707865, 0x3320646e, 0x79622d32, 0x6b206574];

        // State.
        this.keyWords = []; // key words
        this.nonceWords = [0, 0]; // nonce words
        this.counterWords = [0, 0]; // block counter words

        // Output buffer.
        this.block = []; // output block of 64 bytes
        this.blockUsed = 64; // number of block bytes used

        this.setKey(key);
        this.setNonce(nonce);
    }

    // setKey sets the key to the given 32-byte array.
    Salsa20.prototype.setKey = function (key) {
        for (var i = 0, j = 0; i < 8; i++, j += 4) {
            this.keyWords[i] = (key[j] & 0xff) |
            ((key[j + 1] & 0xff) << 8) |
            ((key[j + 2] & 0xff) << 16) |
            ((key[j + 3] & 0xff) << 24);
        }
        this._reset();
    };

    // setNonce sets the nonce to the given 8-byte array.
    Salsa20.prototype.setNonce = function (nonce) {
        this.nonceWords[0] = (nonce[0] & 0xff) |
        ((nonce[1] & 0xff) << 8) |
        ((nonce[2] & 0xff) << 16) |
        ((nonce[3] & 0xff) << 24);
        this.nonceWords[1] = (nonce[4] & 0xff) |
        ((nonce[5] & 0xff) << 8) |
        ((nonce[6] & 0xff) << 16) |
        ((nonce[7] & 0xff) << 24);
        this._reset();
    };

    // getBytes returns the next numberOfBytes bytes of stream.
    Salsa20.prototype.getBytes = function (numberOfBytes) {
        var out = new Array(numberOfBytes);
        for (var i = 0; i < numberOfBytes; i++) {
            if (this.blockUsed == 64) {
                this._generateBlock();
                this._incrementCounter();
                this.blockUsed = 0;
            }
            out[i] = this.block[this.blockUsed];
            this.blockUsed++;
        }
        return out;
    };

    Salsa20.prototype.getHexString = function (numberOfBytes) {
        var hex = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];
        var out = [];
        var bytes = this.getBytes(numberOfBytes);
        for (var i = 0; i < bytes.length; i++) {
            out.push(hex[(bytes[i] >> 4) & 15]);
            out.push(hex[bytes[i] & 15]);
        }
        return out.join('');
    };

    // Private methods.

    Salsa20.prototype._reset = function () {
        this.counterWords[0] = 0;
        this.counterWords[1] = 0;
        this.blockUsed = 64;
    };

    // _incrementCounter increments block counter.
    Salsa20.prototype._incrementCounter = function () {
        // Note: maximum 2^64 blocks.
        this.counterWords[0] = (this.counterWords[0] + 1) & 0xffffffff;
        if (this.counterWords[0] == 0) {
            this.counterWords[1] = (this.counterWords[1] + 1) & 0xffffffff;
        }
    };

    // _generateBlock generates 64 bytes from key, nonce, and counter,
    // and puts the result into this.block.
    Salsa20.prototype._generateBlock = function () {
        var j0 = this.sigmaWords[0],
        j1 = this.keyWords[0],
        j2 = this.keyWords[1],
        j3 = this.keyWords[2],
        j4 = this.keyWords[3],
        j5 = this.sigmaWords[1],
        j6 = this.nonceWords[0],
        j7 = this.nonceWords[1],
        j8 = this.counterWords[0],
        j9 = this.counterWords[1],
        j10 = this.sigmaWords[2],
        j11 = this.keyWords[4],
        j12 = this.keyWords[5],
        j13 = this.keyWords[6],
        j14 = this.keyWords[7],
        j15 = this.sigmaWords[3];

        var x0 = j0, x1 = j1, x2 = j2, x3 = j3, x4 = j4, x5 = j5, x6 = j6, x7 = j7,
        x8 = j8, x9 = j9, x10 = j10, x11 = j11, x12 = j12, x13 = j13, x14 = j14, x15 = j15;

        var u;

        for (var i = 0; i < this.rounds; i += 2) {
            u = x0 + x12;
            x4 ^= (u << 7) | (u >>> (32 - 7));
            u = x4 + x0;
            x8 ^= (u << 9) | (u >>> (32 - 9));
            u = x8 + x4;
            x12 ^= (u << 13) | (u >>> (32 - 13));
            u = x12 + x8;
            x0 ^= (u << 18) | (u >>> (32 - 18));

            u = x5 + x1;
            x9 ^= (u << 7) | (u >>> (32 - 7));
            u = x9 + x5;
            x13 ^= (u << 9) | (u >>> (32 - 9));
            u = x13 + x9;
            x1 ^= (u << 13) | (u >>> (32 - 13));
            u = x1 + x13;
            x5 ^= (u << 18) | (u >>> (32 - 18));

            u = x10 + x6;
            x14 ^= (u << 7) | (u >>> (32 - 7));
            u = x14 + x10;
            x2 ^= (u << 9) | (u >>> (32 - 9));
            u = x2 + x14;
            x6 ^= (u << 13) | (u >>> (32 - 13));
            u = x6 + x2;
            x10 ^= (u << 18) | (u >>> (32 - 18));

            u = x15 + x11;
            x3 ^= (u << 7) | (u >>> (32 - 7));
            u = x3 + x15;
            x7 ^= (u << 9) | (u >>> (32 - 9));
            u = x7 + x3;
            x11 ^= (u << 13) | (u >>> (32 - 13));
            u = x11 + x7;
            x15 ^= (u << 18) | (u >>> (32 - 18));

            u = x0 + x3;
            x1 ^= (u << 7) | (u >>> (32 - 7));
            u = x1 + x0;
            x2 ^= (u << 9) | (u >>> (32 - 9));
            u = x2 + x1;
            x3 ^= (u << 13) | (u >>> (32 - 13));
            u = x3 + x2;
            x0 ^= (u << 18) | (u >>> (32 - 18));

            u = x5 + x4;
            x6 ^= (u << 7) | (u >>> (32 - 7));
            u = x6 + x5;
            x7 ^= (u << 9) | (u >>> (32 - 9));
            u = x7 + x6;
            x4 ^= (u << 13) | (u >>> (32 - 13));
            u = x4 + x7;
            x5 ^= (u << 18) | (u >>> (32 - 18));

            u = x10 + x9;
            x11 ^= (u << 7) | (u >>> (32 - 7));
            u = x11 + x10;
            x8 ^= (u << 9) | (u >>> (32 - 9));
            u = x8 + x11;
            x9 ^= (u << 13) | (u >>> (32 - 13));
            u = x9 + x8;
            x10 ^= (u << 18) | (u >>> (32 - 18));

            u = x15 + x14;
            x12 ^= (u << 7) | (u >>> (32 - 7));
            u = x12 + x15;
            x13 ^= (u << 9) | (u >>> (32 - 9));
            u = x13 + x12;
            x14 ^= (u << 13) | (u >>> (32 - 13));
            u = x14 + x13;
            x15 ^= (u << 18) | (u >>> (32 - 18));
        }

        x0 += j0;
        x1 += j1;
        x2 += j2;
        x3 += j3;
        x4 += j4;
        x5 += j5;
        x6 += j6;
        x7 += j7;
        x8 += j8;
        x9 += j9;
        x10 += j10;
        x11 += j11;
        x12 += j12;
        x13 += j13;
        x14 += j14;
        x15 += j15;

        this.block[0] = (x0 >>> 0) & 0xff; this.block[1] = (x0 >>> 8) & 0xff;
        this.block[2] = (x0 >>> 16) & 0xff; this.block[3] = (x0 >>> 24) & 0xff;
        this.block[4] = (x1 >>> 0) & 0xff; this.block[5] = (x1 >>> 8) & 0xff;
        this.block[6] = (x1 >>> 16) & 0xff; this.block[7] = (x1 >>> 24) & 0xff;
        this.block[8] = (x2 >>> 0) & 0xff; this.block[9] = (x2 >>> 8) & 0xff;
        this.block[10] = (x2 >>> 16) & 0xff; this.block[11] = (x2 >>> 24) & 0xff;
        this.block[12] = (x3 >>> 0) & 0xff; this.block[13] = (x3 >>> 8) & 0xff;
        this.block[14] = (x3 >>> 16) & 0xff; this.block[15] = (x3 >>> 24) & 0xff;
        this.block[16] = (x4 >>> 0) & 0xff; this.block[17] = (x4 >>> 8) & 0xff;
        this.block[18] = (x4 >>> 16) & 0xff; this.block[19] = (x4 >>> 24) & 0xff;
        this.block[20] = (x5 >>> 0) & 0xff; this.block[21] = (x5 >>> 8) & 0xff;
        this.block[22] = (x5 >>> 16) & 0xff; this.block[23] = (x5 >>> 24) & 0xff;
        this.block[24] = (x6 >>> 0) & 0xff; this.block[25] = (x6 >>> 8) & 0xff;
        this.block[26] = (x6 >>> 16) & 0xff; this.block[27] = (x6 >>> 24) & 0xff;
        this.block[28] = (x7 >>> 0) & 0xff; this.block[29] = (x7 >>> 8) & 0xff;
        this.block[30] = (x7 >>> 16) & 0xff; this.block[31] = (x7 >>> 24) & 0xff;
        this.block[32] = (x8 >>> 0) & 0xff; this.block[33] = (x8 >>> 8) & 0xff;
        this.block[34] = (x8 >>> 16) & 0xff; this.block[35] = (x8 >>> 24) & 0xff;
        this.block[36] = (x9 >>> 0) & 0xff; this.block[37] = (x9 >>> 8) & 0xff;
        this.block[38] = (x9 >>> 16) & 0xff; this.block[39] = (x9 >>> 24) & 0xff;
        this.block[40] = (x10 >>> 0) & 0xff; this.block[41] = (x10 >>> 8) & 0xff;
        this.block[42] = (x10 >>> 16) & 0xff; this.block[43] = (x10 >>> 24) & 0xff;
        this.block[44] = (x11 >>> 0) & 0xff; this.block[45] = (x11 >>> 8) & 0xff;
        this.block[46] = (x11 >>> 16) & 0xff; this.block[47] = (x11 >>> 24) & 0xff;
        this.block[48] = (x12 >>> 0) & 0xff; this.block[49] = (x12 >>> 8) & 0xff;
        this.block[50] = (x12 >>> 16) & 0xff; this.block[51] = (x12 >>> 24) & 0xff;
        this.block[52] = (x13 >>> 0) & 0xff; this.block[53] = (x13 >>> 8) & 0xff;
        this.block[54] = (x13 >>> 16) & 0xff; this.block[55] = (x13 >>> 24) & 0xff;
        this.block[56] = (x14 >>> 0) & 0xff; this.block[57] = (x14 >>> 8) & 0xff;
        this.block[58] = (x14 >>> 16) & 0xff; this.block[59] = (x14 >>> 24) & 0xff;
        this.block[60] = (x15 >>> 0) & 0xff; this.block[61] = (x15 >>> 8) & 0xff;
        this.block[62] = (x15 >>> 16) & 0xff; this.block[63] = (x15 >>> 24) & 0xff;
    };


    return Salsa20;
})();