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Created October 23, 2014 19:57
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SHA-1 implementation in JavaScript
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* SHA-1 implementation in JavaScript (c) Chris Veness 2002-2014 */
/* */
/* - see http://csrc.nist.gov/groups/ST/toolkit/secure_hashing.html */
/* http://csrc.nist.gov/groups/ST/toolkit/examples.html */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* jshint node:true *//* global define, escape, unescape */
'use strict';
/**
* SHA-1 hash function reference implementation.
*
* @namespace
*/
var Sha1 = {};
/**
* Generates SHA-1 hash of string.
*
* @param {string} msg - (Unicode) string to be hashed.
* @returns {string} Hash of msg as hex character string.
*/
Sha1.hash = function(msg) {
// convert string to UTF-8, as SHA only deals with byte-streams
msg = msg.utf8Encode();
// constants [§4.2.1]
var K = [ 0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6 ];
// PREPROCESSING
msg += String.fromCharCode(0x80); // add trailing '1' bit (+ 0's padding) to string [§5.1.1]
// convert string msg into 512-bit/16-integer blocks arrays of ints [§5.2.1]
var l = msg.length/4 + 2; // length (in 32-bit integers) of msg + ‘1’ + appended length
var N = Math.ceil(l/16); // number of 16-integer-blocks required to hold 'l' ints
var M = new Array(N);
for (var i=0; i<N; i++) {
M[i] = new Array(16);
for (var j=0; j<16; j++) { // encode 4 chars per integer, big-endian encoding
M[i][j] = (msg.charCodeAt(i*64+j*4)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16) |
(msg.charCodeAt(i*64+j*4+2)<<8) | (msg.charCodeAt(i*64+j*4+3));
} // note running off the end of msg is ok 'cos bitwise ops on NaN return 0
}
// add length (in bits) into final pair of 32-bit integers (big-endian) [§5.1.1]
// note: most significant word would be (len-1)*8 >>> 32, but since JS converts
// bitwise-op args to 32 bits, we need to simulate this by arithmetic operators
M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32); M[N-1][14] = Math.floor(M[N-1][14]);
M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;
// set initial hash value [§5.3.1]
var H0 = 0x67452301;
var H1 = 0xefcdab89;
var H2 = 0x98badcfe;
var H3 = 0x10325476;
var H4 = 0xc3d2e1f0;
// HASH COMPUTATION [§6.1.2]
var W = new Array(80); var a, b, c, d, e;
for (var i=0; i<N; i++) {
// 1 - prepare message schedule 'W'
for (var t=0; t<16; t++) W[t] = M[i][t];
for (var t=16; t<80; t++) W[t] = Sha1.ROTL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);
// 2 - initialise five working variables a, b, c, d, e with previous hash value
a = H0; b = H1; c = H2; d = H3; e = H4;
// 3 - main loop
for (var t=0; t<80; t++) {
var s = Math.floor(t/20); // seq for blocks of 'f' functions and 'K' constants
var T = (Sha1.ROTL(a,5) + Sha1.f(s,b,c,d) + e + K[s] + W[t]) & 0xffffffff;
e = d;
d = c;
c = Sha1.ROTL(b, 30);
b = a;
a = T;
}
// 4 - compute the new intermediate hash value (note 'addition modulo 2^32')
H0 = (H0+a) & 0xffffffff;
H1 = (H1+b) & 0xffffffff;
H2 = (H2+c) & 0xffffffff;
H3 = (H3+d) & 0xffffffff;
H4 = (H4+e) & 0xffffffff;
}
return Sha1.toHexStr(H0) + Sha1.toHexStr(H1) + Sha1.toHexStr(H2) +
Sha1.toHexStr(H3) + Sha1.toHexStr(H4);
};
/**
* Function 'f' [§4.1.1].
* @private
*/
Sha1.f = function(s, x, y, z) {
switch (s) {
case 0: return (x & y) ^ (~x & z); // Ch()
case 1: return x ^ y ^ z; // Parity()
case 2: return (x & y) ^ (x & z) ^ (y & z); // Maj()
case 3: return x ^ y ^ z; // Parity()
}
};
/**
* Rotates left (circular left shift) value x by n positions [§3.2.5].
* @private
*/
Sha1.ROTL = function(x, n) {
return (x<<n) | (x>>>(32-n));
};
/**
* Hexadecimal representation of a number.
* @private
*/
Sha1.toHexStr = function(n) {
// note can't use toString(16) as it is implementation-dependant,
// and in IE returns signed numbers when used on full words
var s="", v;
for (var i=7; i>=0; i--) { v = (n>>>(i*4)) & 0xf; s += v.toString(16); }
return s;
};
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/** Extend String object with method to encode multi-byte string to utf8
* - monsur.hossa.in/2012/07/20/utf-8-in-javascript.html */
if (typeof String.prototype.utf8Encode == 'undefined') {
String.prototype.utf8Encode = function() {
return unescape( encodeURIComponent( this ) );
};
}
/** Extend String object with method to decode utf8 string to multi-byte */
if (typeof String.prototype.utf8Decode == 'undefined') {
String.prototype.utf8Decode = function() {
try {
return decodeURIComponent( escape( this ) );
} catch (e) {
return this; // invalid UTF-8? return as-is
}
};
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
if (typeof module != 'undefined' && module.exports) module.exports = Sha1; // CommonJs export
if (typeof define == 'function' && define.amd) define([], function() { return Sha1; }); // AMD
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