JavaScript实现SHA-1加密算法的方法

/
 
  A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined
  in FIPS PUB 180-1
 
  By lizq
 
  2006-11-11
 
 /
/
 
  Configurable variables.
 
 /
var hexcase = 0; / hex output format. 0 - lowercase; 1 - uppercase /
var chrsz = 8; / bits per input character. 8 - ASCII; 16 - Unicode /
/
 
  The main function to calculate message digest
 
 /
function hex_sha1(s){
    return binb2hex(core_sha1(AlignSHA1(s)));
}
/
 
  Perform a simple self-test to see if the VM is working
 
 /
function sha1_vm_test(){
    return hex_sha1("abc") == "a9993e364706816aba3e25717850c26c9cd0d89d";
}
/
 
  Calculate the SHA-1 of an array of big-endian words, and a bit length
 
 /
function core_sha1(blockArray){
    var x = blockArray; // append padding
    var w = Array(80);
    var a = 1732584193;
    var b = -271733879;
    var c = -1732584194;
    var d = 271733878;
    var e = -1009589776;
    for (var i = 0; i < x.length; i += 16) // 每次处理512位 1632
    {
        var olda = a;
        var oldb = b;
        var oldc = c;
        var oldd = d;
        var olde = e;
        for (var j = 0; j < 80; j++) // 对每个512位进行80步操作
        {
            if (j < 16)
                w[j] = x[i + j];
            else
                w[j] = rol(w[j - 3] ^ w[j - 8] ^ w[j - 14] ^ w[j - 16], 1);
            var t = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)), safe_add(safe_add(e, w[j]), sha1_kt(j)));
            e = d;
            d = c;
            c = rol(b, 30);
            b = a;
            a = t;
        }
        a = safe_add(a, olda);
        b = safe_add(b, oldb);
        c = safe_add(c, oldc);
        d = safe_add(d, oldd);
        e = safe_add(e, olde);
    }
    return new Array(a, b, c, d, e);
}
/
 
  Perform the appropriate triplet bination function for the current
  iteration
 
  返回对应F函数的值
 
 /
function sha1_ft(t, b, c, d){
    if (t < 20)
        return (b & c) | ((~ b) & d);
    if (t < 40)
        return b ^ c ^ d;
    if (t < 60)
        return (b & c) | (b & d) | (c & d);
    return b ^ c ^ d; // t<80
}
/
 
  Determine the appropriate additive constant for the current iteration
 
  返回对应的Kt值
 
 /
function sha1_kt(t){
    return (t < 20) ? 1518500249 : (t < 40) ? 1859775393 : (t < 60) ? -1894007588 : -899497514;
}
/
 
  Add integers, wrapping at 2^32. This uses 16-bit operations internally
 
  to work around bugs in some JS interpreters.
 
  将32位数拆成高16位和低16位分别进行相加，从而实现 MOD 2^32 的加法
 
 /
function safe_add(x, y){
    var lsw = (x & 0xFFFF) + (y & 0xFFFF);
    var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
    return (msw << 16) | (lsw & 0xFFFF);
}
/
 
  Bitwise rotate a 32-bit number to the left.
 
  32位二进制数循环左移
 
 /
function rol(num, t){
    return (num << t) | (num >>> (32 - t));
}
/
 
  The standard SHA1 needs the input string to fit into a block
 
  This function align the input string to meet the requirement
 
 /
function AlignSHA1(str){
    var nblk = ((str.length + 8) >> 6) + 1, blks = new Array(nblk 16);
    for (var i = 0; i < nblk 16; i++)
        blks[i] = 0;
    for (i = 0; i < str.length; i++)
        blks[i >> 2] |= str.charCodeAt(i) << (24 - (i & 3) 8);
    blks[i >> 2] |= 0x80 << (24 - (i & 3) 8);
    blks[nblk 16 - 1] = str.length 8;
    return blks;
}
/
 
  Convert an array of big-endian words to a hex string.
 
 /
function binb2hex(binarray){
    var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
    var str = "";
    for (var i = 0; i < binarray.length 4; i++) {
        str += hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) 8 + 4)) & 0xF) +
        hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) 8)) & 0xF);
    }
    return str;
}
/
 
  calculate MessageDigest aord to source message that inputted
 
 /
function calcDigest(){
    var digestM = hex_sha1(document.SHAForm.SourceMessage.value);
    document.SHAForm.MessageDigest.value = digestM;
}