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<title>One-Time Pad Generator</title>
<meta name="description" content="JavaScript One-Time Pad Generator" />
<meta name="author" content="John Walker" />
<meta name="keywords" content="one, time, pad, generator, onetime, cryptography, JavaScript" />
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<script type="text/javascript">
//<![CDATA[

    loadTime = (new Date()).getTime();

/*

    L'Ecuyer's two-sequence generator with a Bays-Durham shuffle
    on the back-end.  Schrage's algorithm is used to perform
    64-bit modular arithmetic within the 32-bit constraints of
    JavaScript.

    Bays, C. and S. D. Durham.  ACM Trans. Math. Software: 2 (1976)
        59-64.

    L'Ecuyer, P.  Communications of the ACM: 31 (1968) 742-774.

    Schrage, L.  ACM Trans. Math. Software: 5 (1979) 132-138.

*/

function uGen(old, a, q, r, m) {      // Schrage's modular multiplication algorithm
    var t;

    t = Math.floor(old / q);
    t = a * (old - (t * q)) - (t * r);
    return Math.round((t < 0) ? (t + m) : t);
}

function LEnext() {                   // Return next raw value
    var i;

    this.gen1 = uGen(this.gen1, 40014, 53668, 12211, 2147483563);
    this.gen2 = uGen(this.gen2, 40692, 52774, 3791, 2147483399);

    /* Extract shuffle table index from most significant part
       of the previous result. */

    i = Math.floor(this.state / 67108862);

    // New state is sum of generators modulo one of their moduli

    this.state = Math.round((this.shuffle[i] + this.gen2) % 2147483563);

    // Replace value in shuffle table with generator 1 result

    this.shuffle[i] = this.gen1;

    return this.state;
}

//  Return next random integer between 0 and n inclusive

function LEnint(n) {
    return Math.floor(this.next() / (1 + 2147483562 / (n + 1)));
}

//  Constructor.  Called with seed value

function LEcuyer(s) {
    var i;

    this.shuffle = new Array(32);
    this.gen1 = this.gen2 = (s & 0x7FFFFFFF);
    for (i = 0; i < 19; i++) {
        this.gen1 = uGen(this.gen1, 40014, 53668, 12211, 2147483563);
    }

    // Fill the shuffle table with values

    for (i = 0; i < 32; i++) {
        this.gen1 = uGen(this.gen1, 40014, 53668, 12211, 2147483563);
        this.shuffle[31 - i] = this.gen1;
    }
    this.state = this.shuffle[0];
    this.next = LEnext;
    this.nextInt = LEnint;
}

function sepchar() {
    if (rsep) {
        var seps = "!#$%&()*+,-./:;<=>?@[]^_{|}~";
        return seps.charAt(sepran.nextInt(seps.length - 1));
    }
    return "-";
}

/*
 *  md5.jvs 1.0b 27/06/96
 *
 * Javascript implementation of the RSA Data Security, Inc. MD5
 * Message-Digest Algorithm.
 *
 * Copyright (c) 1996 Henri Torgemane. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for any purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. 
 *
 * Of course, this soft is provided "as is" without express or implied
 * warranty of any kind.

    This version contains some trivial reformatting modifications
    by John Walker.

 */

function array(n) {
    for (i = 0; i < n; i++) {
        this[i] = 0;
    }
    this.length = n;
}

/* Some basic logical functions had to be rewritten because of a bug in
 * Javascript.. Just try to compute 0xffffffff >> 4 with it..
 * Of course, these functions are slower than the original would be, but
 * at least, they work!
 */

function integer(n) {
    return n % (0xffffffff + 1);
}

function shr(a, b) {
    a = integer(a);
    b = integer(b);
    if (a - 0x80000000 >= 0) {
        a = a % 0x80000000;
        a >>= b;
        a += 0x40000000 >> (b - 1);
    } else {
        a >>= b;
    }
    return a;
}

function shl1(a) {
    a = a % 0x80000000;
    if (a & 0x40000000 == 0x40000000) {
        a -= 0x40000000;  
        a *= 2;
        a += 0x80000000;
    } else {
        a *= 2;
    }
    return a;
}

function shl(a, b) {
    a = integer(a);
    b = integer(b);
    for (var i = 0; i < b; i++) {
        a = shl1(a);
    }
    return a;
}

function and(a, b) {
    a = integer(a);
    b = integer(b);
    var t1 = a - 0x80000000;
    var t2 = b - 0x80000000;
    if (t1 >= 0) {
        if (t2 >= 0) {
            return ((t1 & t2) + 0x80000000);
        } else {
            return (t1 & b);
        }
    } else {
        if (t2 >= 0) {
            return (a & t2);
        } else {
            return (a & b);  
        }
    }
}

function or(a, b) {
    a = integer(a);
    b = integer(b);
    var t1 = a - 0x80000000;
    var t2 = b - 0x80000000;
    if (t1 >= 0) {
        if (t2 >= 0) {
            return ((t1 | t2) + 0x80000000);
        } else {
            return ((t1 | b) + 0x80000000);
        }
    } else {
        if (t2 >= 0) {
            return ((a | t2) + 0x80000000);
        } else {
            return (a | b);  
        }
    }
}

function xor(a, b) {
    a = integer(a);
    b = integer(b);
    var t1 = a - 0x80000000;
    var t2 = b - 0x80000000;
    if (t1 >= 0) {
        if (t2 >= 0) {
            return (t1 ^ t2);
        } else {
            return ((t1 ^ b) + 0x80000000);
        }
    } else {
        if (t2 >= 0) {
            return ((a ^ t2) + 0x80000000);
        } else {
            return (a ^ b);  
        }
    }
}

function not(a) {
    a = integer(a);
    return 0xffffffff - a;
}

/* Here begin the real algorithm */

var state = new array(4); 
var count = new array(2);
    count[0] = 0;
    count[1] = 0;                     
var buffer = new array(64); 
var transformBuffer = new array(16); 
var digestBits = new array(16);

var S11 = 7;
var S12 = 12;
var S13 = 17;
var S14 = 22;
var S21 = 5;
var S22 = 9;
var S23 = 14;
var S24 = 20;
var S31 = 4;
var S32 = 11;
var S33 = 16;
var S34 = 23;
var S41 = 6;
var S42 = 10;
var S43 = 15;
var S44 = 21;

function F(x, y, z) {
    return or(and(x, y), and(not(x), z));
}

function G(x, y, z) {
    return or(and(x, z), and(y, not(z)));
}

function H(x, y, z) {
    return xor(xor(x, y), z);
}

function I(x, y, z) {
    return xor(y ,or(x , not(z)));
}

function rotateLeft(a, n) {
    return or(shl(a, n), (shr(a, (32 - n))));
}

function FF(a, b, c, d, x, s, ac) {
    a = a + F(b, c, d) + x + ac;
    a = rotateLeft(a, s);
    a = a + b;
    return a;
}

function GG(a, b, c, d, x, s, ac) {
    a = a + G(b, c, d) + x + ac;
    a = rotateLeft(a, s);
    a = a + b;
    return a;
}

function HH(a, b, c, d, x, s, ac) {
    a = a + H(b, c, d) + x + ac;
    a = rotateLeft(a, s);
    a = a + b;
    return a;
}

function II(a, b, c, d, x, s, ac) {
    a = a + I(b, c, d) + x + ac;
    a = rotateLeft(a, s);
    a = a + b;
    return a;
}

function transform(buf, offset) { 
    var a = 0, b = 0, c = 0, d = 0; 
    var x = transformBuffer;
    
    a = state[0];
    b = state[1];
    c = state[2];
    d = state[3];
    
    for (i = 0; i < 16; i++) {
        x[i] = and(buf[i * 4 + offset], 0xFF);
        for (j = 1; j < 4; j++) {
            x[i] += shl(and(buf[i * 4 + j + offset] ,0xFF), j * 8);
        }
    }

    /* Round 1 */
    a = FF( a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
    d = FF( d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
    c = FF( c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
    b = FF( b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
    a = FF( a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
    d = FF( d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
    c = FF( c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
    b = FF( b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
    a = FF( a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
    d = FF( d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
    c = FF( c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
    b = FF( b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
    a = FF( a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
    d = FF( d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
    c = FF( c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
    b = FF( b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

    /* Round 2 */
    a = GG( a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
    d = GG( d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
    c = GG( c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
    b = GG( b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
    a = GG( a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
    d = GG( d, a, b, c, x[10], S22,  0x2441453); /* 22 */
    c = GG( c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
    b = GG( b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
    a = GG( a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
    d = GG( d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
    c = GG( c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
    b = GG( b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
    a = GG( a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
    d = GG( d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
    c = GG( c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
    b = GG( b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

    /* Round 3 */
    a = HH( a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
    d = HH( d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
    c = HH( c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
    b = HH( b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
    a = HH( a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
    d = HH( d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
    c = HH( c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
    b = HH( b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
    a = HH( a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
    d = HH( d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
    c = HH( c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
    b = HH( b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
    a = HH( a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
    d = HH( d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
    c = HH( c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
    b = HH( b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

    /* Round 4 */
    a = II( a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
    d = II( d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
    c = II( c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
    b = II( b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
    a = II( a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
    d = II( d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
    c = II( c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
    b = II( b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
    a = II( a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
    d = II( d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
    c = II( c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
    b = II( b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
    a = II( a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
    d = II( d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
    c = II( c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
    b = II( b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;

}

function init() {
    count[0] = count[1] = 0;
    state[0] = 0x67452301;
    state[1] = 0xefcdab89;
    state[2] = 0x98badcfe;
    state[3] = 0x10325476;
    for (i = 0; i < digestBits.length; i++) {
        digestBits[i] = 0;
    }
}

function update(b) { 
    var index, i;
    
    index = and(shr(count[0],3) , 0x3F);
    if (count[0] < 0xFFFFFFFF - 7) {
      count[0] += 8;
    } else {
      count[1]++;
      count[0] -= 0xFFFFFFFF + 1;
      count[0] += 8;
    }
    buffer[index] = and(b, 0xff);
    if (index  >= 63) {
        transform(buffer, 0);
    }
}

function finish() {
    var bits = new array(8);
    var padding; 
    var i = 0, index = 0, padLen = 0;

    for (i = 0; i < 4; i++) {
        bits[i] = and(shr(count[0], (i * 8)), 0xFF);
    }
    for (i = 0; i < 4; i++) {
        bits[i + 4] = and(shr(count[1], (i * 8)), 0xFF);
    }
    index = and(shr(count[0], 3), 0x3F);
    padLen = (index < 56) ? (56 - index) : (120 - index);
    padding = new array(64); 
    padding[0] = 0x80;
    for (i = 0; i < padLen; i++) {
      update(padding[i]);
    }
    for (i = 0; i < 8; i++) {
      update(bits[i]);
    }

    for (i = 0; i < 4; i++) {
        for (j = 0; j < 4; j++) {
            digestBits[i * 4 + j] = and(shr(state[i], (j * 8)) , 0xFF);
        }
    } 
}

/* End of the MD5 algorithm */

function gen() {
    window.status = "Generating...";
    document.getElementById('onetime').pad.value = "";

    lower = document.getElementById('onetime').textcase.selectedIndex == 0;
    upper = document.getElementById('onetime').textcase.selectedIndex == 1;
    mixed = document.getElementById('onetime').textcase.selectedIndex == 2;
    rsep = document.getElementById('onetime').rsep.checked;
    if (!(numeric = document.getElementById('onetime').keytype[0].checked)) {
        english = document.getElementById('onetime').keytype[1].checked;
        gibberish = document.getElementById('onetime').keytype[3].checked;
    }
    clockseed = document.getElementById('onetime').seedy[0].checked
    makesig = document.getElementById('onetime').dosig.checked;
    npass = document.getElementById('onetime').nkeys.value;
    pw_length = Math.round(document.getElementById('onetime').klength.value);
    sep = document.getElementById('onetime').sep.value;
    linelen = document.getElementById('onetime').linelen.value;
//               01234567890123456789012345678901
    charcodes = " " +
                "!\"#$%&'()*+,-./0123456789:;<=>?" +
                "@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_" +
                "`abcdefghijklmnopqrstuvwxyz{|}~";

    if (clockseed) {
        var n, j, ran0;

        /*  Obtain seed from the clock.  To reduce the likelihood
            of the seed being guessed, we create the seed by combining
            the time of the request with the time the page was loaded,
            then use that composite value to seed an auxiliary generator
            which is cycled between one and 32 times based on the time
            derived initial seed, with the output of the generator fed
            back into the seed we use to generate the pad.  */

        seed = Math.round((new Date()).getTime() % Math.pow(2, 31));
        ran0 = new LEcuyer((seed ^ Math.round(loadTime % Math.pow(2, 31))) & 0x7FFFFFFF);
        for (j = 0; j < (5 + ((seed >> 3) & 0xF)); j++) {
            n = ran0.nextInt(31);
        }
        while (n-- >= 0) {
            seed = ((seed << 11) | (seed >>> (32 - 11))) ^ ran0.next();
        }
        seed &= 0x7FFFFFFF;
        document.getElementById('onetime').seeder.value = seed;
    } else {
        var useed, seedNum;

        /* Obtain seed from user specification.  If the seed is a
           decimal number, use it as-is.  If it contains any
           non-numeric characters, construct a hash code and
           use that as the seed. */

        useed = document.getElementById('onetime').seeder.value;
        seedNum = true;
        for (i = 0; i < useed.length; i++) {
            if ("0123456789".indexOf(useed.charAt(i)) == -1) {
                seedNum = false;
                break;
            }
        }
        if (seedNum) {
            seed = Math.round(Math.floor(document.getElementById('onetime').seeder.value) % Math.pow(2, 31));
            document.getElementById('onetime').seeder.value = seed;
        } else {
            var s, t, iso, hex;

            iso = "";
            hex = "0123456789ABCDEF";
            for (i = 32; i < 256; i++) {
                if (i < 127 || i >= 160) {
                    // Why not "s = i.toString(16);"?  Doesn't work in Netscape 3.0
                    iso += "%" + hex.charAt(i >> 4) + hex.charAt(i & 0xF);
                }
            }
            iso = unescape(iso);
            s = 0;
            for (i = 0; i < useed.length; i++) {
                t = iso.indexOf(useed.charAt(i));
                if (t < 0) {
                    t = 17;
                }
                s = 0x7FFFFFFF & (((s << 5) | (s >> (32 - 5))) ^ t);
            }
            seed = s;
        }
    }
    ran1 = new LEcuyer(seed);
    ran2 = new LEcuyer(seed);
    if (rsep) {
        /*  Use a separate random generator for separators
            so that results are the same for a given seed
            for both choices of separators.  */
        sepran = new LEcuyer(seed);
    }

    ndig = 1;
    j = 10;
    while (npass >= j) {
        ndig++;
        j *= 10;
    }
    pw_item = pw_length + (sep > 0 ? (pw_length / sep) : 0);
    pw_item += ndig + 5;
    j = pw_item * 3;
    if (j < 132) {
        j = 132;
    }
    npline = Math.floor(linelen / pw_item);
    if (npline < 1) {
        npline = 0;
    }
    v = "";
    md5v = "";
    lineno = 0;
    if (!numeric) {
        letters = "abcdefghijklmnopqrstuvwxyz";
        if (upper) {
            letters = letters.toUpperCase();
        }
        if (english) {

            // Frequency of English digraphs (from D. Edwards 1/27/66)

            frequency = new Array( 
                new Array(4, 20, 28, 52, 2, 11, 28, 4, 32, 4, 6, 62,
                          23, 167, 2, 14, 0, 83, 76, 127, 7, 25, 8, 1,
                          9, 1), /* aa - az */

                new Array(13, 0, 0, 0, 55, 0, 0, 0, 8, 2, 0, 22, 0, 0,
                          11, 0, 0, 15, 4, 2, 13, 0, 0, 0, 15, 0), /* ba - bz */

                new Array(32, 0, 7, 1, 69, 0, 0, 33, 17, 0, 10, 9, 1,
                          0, 50, 3, 0, 10, 0, 28, 11, 0, 0, 0, 3, 0), /* ca - cz */

                new Array(40, 16, 9, 5, 65, 18, 3, 9, 56, 0, 1, 4, 15,
                          6, 16, 4, 0, 21, 18, 53, 19, 5, 15, 0, 3, 0), /* da - dz */

                new Array(84, 20, 55, 125, 51, 40, 19, 16, 50, 1, 4,
                          55, 54, 146, 35, 37, 6, 191, 149, 65, 9, 26,
                          21, 12, 5, 0), /* ea - ez */

                new Array(19, 3, 5, 1, 19, 21, 1, 3, 30, 2, 0, 11, 1,
                          0, 51, 0, 0, 26, 8, 47, 6, 3, 3, 0, 2, 0), /* fa - fz */

                new Array(20, 4, 3, 2, 35, 1, 3, 15, 18, 0, 0, 5, 1,
                          4, 21, 1, 1, 20, 9, 21, 9, 0, 5, 0, 1, 0), /* ga - gz */

                new Array(101, 1, 3, 0, 270, 5, 1, 6, 57, 0, 0, 0, 3,
                          2, 44, 1, 0, 3, 10, 18, 6, 0, 5, 0, 3, 0), /* ha - hz */

                new Array(40, 7, 51, 23, 25, 9, 11, 3, 0, 0, 2, 38,
                          25, 202, 56, 12, 1, 46, 79, 117, 1, 22, 0,
                          4, 0, 3), /* ia - iz */

                new Array(3, 0, 0, 0, 5, 0, 0, 0, 1, 0, 0, 0, 0, 0, 4,
                          0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0), /* ja - jz */

                new Array(1, 0, 0, 0, 11, 0, 0, 0, 13, 0, 0, 0, 0, 2,
                          0, 0, 0, 0, 6, 2, 1, 0, 2, 0, 1, 0), /* ka - kz */

                new Array(44, 2, 5, 12, 62, 7, 5, 2, 42, 1, 1, 53, 2,
                          2, 25, 1, 1, 2, 16, 23, 9, 0, 1, 0, 33, 0), /* la - lz */

                new Array(52, 14, 1, 0, 64, 0, 0, 3, 37, 0, 0, 0, 7,
                          1, 17, 18, 1, 2, 12, 3, 8, 0, 1, 0, 2, 0), /* ma - mz */

                new Array(42, 10, 47, 122, 63, 19, 106, 12, 30, 1, 6,
                          6, 9, 7, 54, 7, 1, 7, 44, 124, 6, 1, 15, 0,
                          12, 0), /* na - nz */

                new Array(7, 12, 14, 17, 5, 95, 3, 5, 14, 0, 0, 19,
                          41, 134, 13, 23, 0, 91, 23, 42, 55, 16, 28,
                          0, 4, 1), /* oa - oz */

                new Array(19, 1, 0, 0, 37, 0, 0, 4, 8, 0, 0, 15, 1, 0,
                          27, 9, 0, 33, 14, 7, 6, 0, 0, 0, 0, 0), /* pa - pz */

                new Array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                          0, 0, 0, 0, 0, 17, 0, 0, 0, 0, 0), /* qa - qz */

                new Array(83, 8, 16, 23, 169, 4, 8, 8, 77, 1, 10, 5,
                          26, 16, 60, 4, 0, 24, 37, 55, 6, 11, 4, 0,
                          28, 0), /* ra - rz */

                new Array(65, 9, 17, 9, 73, 13, 1, 47, 75, 3, 0, 7,
                          11, 12, 56, 17, 6, 9, 48, 116, 35, 1, 28, 0,
                          4, 0), /* sa - sz */

                new Array(57, 22, 3, 1, 76, 5, 2, 330, 126, 1, 0, 14,
                          10, 6, 79, 7, 0, 49, 50, 56, 21, 2, 27, 0,
                          24, 0), /* ta - tz */

                new Array(11, 5, 9, 6, 9, 1, 6, 0, 9, 0, 1, 19, 5, 31,
                          1, 15, 0, 47, 39, 31, 0, 3, 0, 0, 0, 0), /* ua - uz */

                new Array(7, 0, 0, 0, 72, 0, 0, 0, 28, 0, 0, 0, 0, 0,
                          5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0), /* va - vz */

                new Array(36, 1, 1, 0, 38, 0, 0, 33, 36, 0, 0, 4, 1,
                          8, 15, 0, 0, 0, 4, 2, 0, 0, 1, 0, 0, 0), /* wa - wz */

                new Array(1, 0, 2, 0, 0, 1, 0, 0, 3, 0, 0, 0, 0, 0, 1,
                          5, 0, 0, 0, 3, 0, 0, 1, 0, 0, 0), /* xa - xz */

                new Array(14, 5, 4, 2, 7, 12, 12, 6, 10, 0, 0, 3, 7,
                          5, 17, 3, 0, 4, 16, 30, 0, 0, 5, 0, 0, 0), /* ya - yz */

                new Array(1, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) /* za - zz */ );

            // This MUST be equal to the sum of the equivalent rows above.

            row_sums = new Array(
                796,   160,    284,    401,    1276,   262,    199,    539,    777,    
                16,    39,     351,    243,    751,    662,    181,    17,     683,    
                662,   968,    248,    115,    180,    17,     162,    5
            );

            // Frequencies of starting characters.

            start_freq = new Array(
                1299,  425,    725,    271,    375,    470,    93,     223,    1009,
                24,    20,     355,    379,    319,    823,    618,    21,     317,
                962,   1991,   271,    104,    516,    6,      16,     14
            );

            // This MUST be equal to the sum of all elements in the above array.

            total_sum = 11646;
        }
        if (gibberish) {
            gibber = "abcdefghijklmnopqrstuvwxyz" +
                     "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
                     "0123456789" +
                     "!#$%&()*+,-./:;<=>?@[]^_{|}~";
            if (upper) {
                /*  Convert to upper case, leaving two copies of the
                    alphabet for two reasons: first, to favour letters
                    over gnarl, and second, to change only the letter case
                    when the mode is selected.  */
                gibber = gibber.toUpperCase();
            } else if (lower) {
	    	gibber = gibber.toLowerCase();
	    }
        }
    }
    for (line = 1; line <= npass; line++) {
        password = "";
        if (numeric) {
            for (nchars = 0; nchars < pw_length; nchars++) {
                if ((sep > 0) && ((nchars % sep) == 0) && (nchars > 0)) {
                    password += sepchar();
                }
                password += ran1.nextInt(9);
            }
        } else if (!english) {
            for (nchars = 0; nchars < pw_length; nchars++) {
                if ((sep > 0) && ((nchars % sep) == 0) && (nchars > 0)) {
                    password += sepchar();
                }
                if (gibberish) {
                    password += gibber.charAt(ran1.nextInt(gibber.length - 1));
                } else {
                    password += letters.charAt(ran1.nextInt(25));
                }
            }
        } else {
            position = ran1.nextInt(total_sum - 1);
            for (row_position = 0, j = 0; position >= row_position;
                 row_position += start_freq[j], j++) {
                continue;
            }

            password = letters.charAt(i = j - 1);
            nch = 1;
            for (nchars = pw_length - 1; nchars; --nchars) {

                // Now find random position within the row.

                position = ran1.nextInt(row_sums[i] - 1);
                for (row_position = 0, j = 0;
                     position >= row_position;
                     row_position += frequency[i][j], j++) {
                }

                if ((sep > 0) && ((nch % sep) == 0)) {
                    password += sepchar();
                }
                nch++;
                password += letters.charAt(i = j - 1);
            }
        }
	
	if ((!numeric) && (!gibberish) && mixed) {
	    var pwm = '';
	    var j;
	    for (j = 0; j < password.length; j++) {
	    	pwm += ran2.nextInt(1) ? (password.charAt(j)) : (password.charAt(j).toUpperCase());
	    }
	    password = pwm;
	}

        /*  If requested, calculate the MD5 signature for this key and
            and save for later appending to the results.  */

        if (makesig) {
            var n, m, hex = "0123456789ABCDEF";

            init();
            for (m = 0; m < password.length; m++) {
                update(32 + charcodes.indexOf(password.charAt(m)));
            }
            finish();

            for (n = 0; n < 16; n++) {
                md5v += hex.charAt(digestBits[n] >> 4);
                md5v += hex.charAt(digestBits[n] & 0xF);
            }
            md5v += "\n";
        }

        aline = "" + line;
        while (aline.length < ndig) {
            aline = " " + aline;
        }
        v += aline + ") " + password;

        if ((++lineno) >= npline) {
            v += "\n";
            lineno = 0;
        } else {
            v += "  ";
        }
    }

    if (makesig) {
        v += "\n----------  MD5 Signatures  ----------\n" + md5v;
    }

    document.getElementById('onetime').pad.value = v;
    window.status = "Done.";
}

function loadHandler() {
    for (var i = 0; i < 25; i++) {
	gen();
    }
};

//]]>
</script>

</head>

<body class="jsgen" onload="loadHandler();">

<h1><img src="key.gif" class="keyicon" alt=""
    	 width="40" height="40" /> &nbsp; One-Time Pad Generator</h1>

<p>
This page, which requires that your browser support JavaScript
(see <a href="#why"><cite>Why JavaScript</cite></a> below),
generates one-time pads or password lists in a variety of
forms.  It is based a high-quality pseudorandom sequence
generator, which can be seeded either from the current date
and time, or from a seed you provide.  Fill in the form below
to select the format of the pad and press &ldquo;Generate&rdquo; to
create the pad in the text box.  You can then copy and paste
the generated pad into another window to use as you wish.
Each of the labels on the request form is linked to a description
of that parameter.
</p>

<form id="onetime" action="#" onsubmit="return false;">

<p class="centre">
<b>Output:</b>
<a href="#NumberOfKeys">Number of keys</a>: <input type="text" name="nkeys" value="20" size="4" maxlength="12" />
<a href="#LineLength">Line length</a>: <input type="text" name="linelen" value="48" size="3" maxlength="12" />
<br />
<b>Format:</b>
<a href="#KeyLength">Key length</a>: <input type="text" name="klength" value="8" size="3" maxlength="12" />
<a href="#GroupLength">Group length</a>: <input type="text" name="sep" value="4" size="2" maxlength="12" />

<br />
<b>Composition:</b>
<a href="#KeyText">Key text</a>: <input type="radio" name="keytype" /> Numeric
<input type="radio" name="keytype" /> Word-like
<input type="radio" name="keytype" checked="checked" /> Alphabetic
<input type="radio" name="keytype" /> Gibberish
<br />
<a href="#LetterCase">Letters:</a>
<select size="i" name="textcase">

    <option value="1" selected="selected">Lower case</option>
    <option value="2">Upper case</option>
    <option value="3">Mixed case</option>
</select>

<input type="checkbox" name="rsep" /> <a href="#RandomSep">Random separators</a>
<input type="checkbox" name="dosig" /> <a href="#Signatures">Include signatures</a>

<br />
<b><a href="#Seed">Seed:</a></b>
<input type="radio" name="seedy" checked="checked" /> From clock
<input type="radio" name="seedy" /> User-defined:
<input type="text" name="seeder" value="" size="12" maxlength="128" 
       onchange="document.getElementById('onetime').seedy[1].checked=true;" />
<br />
<input type="button" value=" Generate " onclick="gen();" />
&nbsp;
<input type="button" value=" Clear " onclick="document.getElementById('onetime').pad.value = '';" />
&nbsp;
<input type="button" value=" Select " onclick="document.getElementById('onetime').pad.select();" /><br />
<textarea name="pad" rows="12" cols="72">

Uh, oh.  It appears your browser either does not support
JavaScript or that JavaScript has been disabled.  You'll
have to replace your browser with one supporting JavaScript
(or enable it, if that's the problem) before you can use
this page.
</textarea>
</p>

</form>

<script type="text/javascript">
//<![CDATA[
    //  Clear out "sorry, no JavaScript" message from text box.
    document.getElementById('onetime').pad.value = "";
//]]>
</script>

<h2><a name="details">Details</a></h2>

<p>
Each of the fields in the one-time pad request form is described
below.
</p>

<h3><a name="output">Output</a></h3>

<h4><a name="NumberOfKeys">Number of keys</a></h4>

<p>
Enter the number of keys you'd like to generate.  If you generate
more than fit in the results text box, you can use the scroll
bar to view the additional lines.
</p>

<h4><a name="LineLength">Line length</a></h4>

<p>
Lines in the output will be limited to the given length (or contain
only one key if the line length is less than required for a single
key).  If the line length is greater than the width of the results
box, you can use the horizontal scroll bar to view the rest of the
line.  Enter <tt>0</tt> to force one key per line; this is handy
when you're preparing a list of keys to be read by a computer program.
</p>

<h3><a name="format">Format</a></h3>

<h4><a name="KeyLength">Key length</a></h4>

<p>
Each key will contain this number of characters, not counting
separators between groups.
</p>

<h4><a name="GroupLength">Group length</a></h4>

<p>
If a nonzero value is entered in this field, the key will be broken
into groups of the given number of characters by separators.  Humans
find it easier to read and remember sequences of characters when
divided into groups of five or fewer characters.
</p>

<h3><a name="composition">Composition</a></h3>

<h4><a name="KeyText">Key text</a></h4>

<p>
This set of radio buttons lets you select the character set used in
the keys.  The alternatives are listed in order of
increasing security.
</p>

<blockquote>
<dl>
<dt><b>Numeric</b></dt>
<dd>Keys contain only the decimal digits &ldquo;0&rdquo; through &ldquo;9&rdquo;.
    <em>Least secure.</em></dd>

<dt><b>Word-like</b></dt>
<dd>Keys are composed of alphabetic characters which obey the
    digraph statistics of English text.  Such keys contain
    sequences of vowels and consonants familiar to speakers
    of Western languages, and are therefore usually easier to
    memorise but, for a given key length, are less secure than
    purely random letters.</dd>

<dt><b>Alphabetic</b></dt>
<dd>Keys consist of letters of the alphabet chosen at random. 
    Each character has an equal probability of being one of
    the 26 letters.</dd>

<dt><b>Gibberish</b></dt>
<dd>Keys use most of the printable ASCII character set, excluding
    only characters frequently used for quoting purposes.  This
    option provides the greatest security for a given key length,
    but most people find keys like this difficult to memorise or
    even transcribe from a printed pad.  If a human is in the loop,
    it's often better to use a longer alphabetic or word-like key.
    <em>Most secure.</em></dd>
</dl>

</blockquote>

<h4><a name="LetterCase">Letters</a></h4>

<p>
The case of letters in keys generated with Word-like, Alphabetic, and
Gibberish key text will be as chosen.  Most people find it easier to
read lower case letters than all capitals, but for some applications
(for example, where keys must be scanned optically by hardware that
only recognises capital letters), capitals are required.  Selecting
&ldquo;Mixed&nbsp;case&rdquo; creates keys with a mix of upper- and
lower-case letters; such keys are more secure than those with uniform
letter case, but do not pass the &ldquo;telephone test&rdquo;: you
can't read them across a (hopefully secure) voice link without having
to indicate whether each letter is or is not a capital.
</p>

<h4><a name="RandomSep">Random separators</a></h4>

<p>
When the <a href="#KeyLength">Key length</a> is longer than
a nonzero <a href="#GroupLength">Group length</a> specification,
the key is divided into sequences of the given group length
by separator characters.  By default, a hyphen, &ldquo;<tt>-</tt>&rdquo;, is used
to separate groups.  If you check this box, separators will be
chosen at random among punctuation marks generally acceptable
for applications such as passwords.  If you're generating passwords
for a computer system, random separators dramatically increase
the difficulty of guessing passwords by exhaustive search.
</p>

<h4><a name="Signatures">Include signatures</a></h4>

<p>

When this box is checked, at the end of the list of keys, preceded by
a line beginning with ten dashes &ldquo;<tt>-</tt>&rdquo;, the 128 bit MD5 signature of
each key is given, one per line, with signatures expressed as 32
hexadecimal digits.  Key signatures can be used to increase security
when keys are used to control access to computer systems or databases.
Instead of storing a copy of the keys, the computer stores their
signatures.  When the user enters a key, its signature is computed
with the same MD5 algorithm used to generate it initially, and the key
is accepted only if the signature matches.  Since discovering
a key which will generate a given signature is believed to be
computationally prohibitive, even if the list of signatures stored on
the computer is compromised, that information will not permit an
intruder to deduce a valid key.
</p>

<p>
Signature calculation is a computationally intense process for which
JavaScript is not ideally suited; be patient while signatures are
generated, especially if your computer has modest
processing speed.
</p>

<p>
For signature-based validation to be secure, it is essential
the original keys be long enough to prohibit discovery of matching
signatures by exhaustive search.  Suppose, for example, one used
four digit numeric keys, as used for Personal Identification
Numbers (PINs) by many credit card systems.  Since only 10,000
different keys exist, one could simply compute the signatures of
every possible key from 0000 through 9999, permitting an attacker who
came into possession of the table of signatures to recover the
keys by a simple lookup process.  For maximum security, keys must
contain at least as much information as the 128 bit signatures
computed from them.  This implies a minimum key length (not counting
non-random separator characters) for the various key formats as
follows:
</p>

<table class="c" border="border" cellpadding="4">
<tr><th>Key Composition</th> <th>Minimum Characters</th></tr>

<tr><td>Numeric</td> <td class="c">39</td></tr>
<tr><td>Word-like</td> <td class="c">30</td></tr>
<tr><td>Alphabetic</td> <td class="c">28</td></tr>
<tr><td>Gibberish</td> <td class="c">20</td></tr>
</table>

<p>
It should be noted that for many practical applications there is no
need for anything approaching 128-bit security.  The guidelines above
apply only in the case where maximum protection in the event of
undetected compromise of key signatures occurs.  In many
cases, much shorter keys are acceptable, especially when it is assumed
that a compromise of the system's password or signature database would
be only part of a much more serious subversion of all resources
on the system.
</p>

<h3><a name="Seed">Seed</a></h3>

<p>
The <em>seed</em> is the starting value which determines all
subsequent values in the pseudorandom sequence used to generate
the one-time pad.  Given the seed, the pad can be reproduced.  The
seed is a 31-bit number which can be derived from the date and
time at which the one-time pad was requested, or from a
user-defined seed value.  If the user-defined seed consists
entirely of decimal digits, it is used directly as the seed,
modulo 2<sup>31</sup>; if a string containing non-digit characters
is entered, it is used to compute a <em>hash code</em> which is
used to seed the generator.

</p>

<p>
When the clock is used to create the seed, the seed value is entered
in the User-defined box to allow you, by checking &ldquo;User-defined&rdquo;,
to produce additional pads with the same seed.
</p>

<h2><a name="why">Why JavaScript?</a></h2>

<p>
At first glance, JavaScript may seem an odd choice for programming
a page such as this.  The one-time pad generator program is rather
large and complicated, and downloading it to your browser takes longer
than would be required for a Java applet or to transfer a
one-time pad generated by a CGI program on the Web server.  I chose
JavaScript for two reasons: <em>security</em> and <em>transparency</em>.

</p>

<p>
<b>Security.</b>
The sole reason for the existence of one-time pads is to
provide a source of information known only to people to whom
they have been distributed in a secure manner.  This means
the generation process cannot involve any link whose security
is suspect.  If the pad were generated on a Web server and
transmitted to you, it would have to pass over the
Internet, where any intermediate site might make a copy
of your pad before you even received it.  Even if some
mechanism such as encryption could absolutely prevent the
pad's being intercepted, you'd still have no way to be sure
the site generating the pad didn't keep a copy
in a file, conveniently tagged with your Internet address.
</p>

<p>
In order to have any degree of security, it is essential
that the pad be generated on <em>your</em> computer, without
involving any transmission or interaction with other
sites on the Internet.  A Web browser with JavaScript makes
this possible, since the generation program embedded in this
page runs entirely on your own computer and does not
transmit anything over the Internet.  Its output appears
only in the text box, allowing you to cut and paste it
to another application.  From there on, its security is
up to you.
</p>

<p>
Security is never absolute.  A one-time pad generated with
this page might be compromised in a variety of ways, including
the following:

</p>

<ul>
<li>    Your Web browser and/or JavaScript interpreter may
        contain bugs or deliberate security violations
        which report activity on your computer back to some
        other Internet site.</li>

<li>    Some other applet running on another page of your
        browser, perhaps without your being aware of its
        existence, is spying on other windows.</li>

<li>    Some other application running on your computer
        may have compromised your system's security and
        be snooping on your activity.</li>

<li>    Your Web browser may be keeping a &ldquo;history log&rdquo;

        or &ldquo;cache&rdquo; of data you generate.  Somebody may
        come along later and recover a copy of the pad
        from that log.</li>

<li>    The implementation of this page may contain a bug
        or deliberate error which makes its output
        predictable.  This is why <a href="#trans"><cite>transparency</cite></a>,
        discussed below, is essential.</li>

<li>    Your computer's security may have been compromised
        physically; when's the last time you checked that a
        bug that transmits your keystrokes and/or screen
        contents to that white van parked down the street
        wasn't lurking inside your computer cabinet?</li>
</ul>

<p>
One can whip oneself into a fine fever of paranoia worrying about
things like this.  One way to rule out the most probable risks
is to download a copy of the generator page and run it
from a &ldquo;<tt>file:</tt>&rdquo; URL on a computer which has no network
connection whatsoever and is located in a secure location
under your control.  And look very carefully at any files
created by your Web browser.  You may find the most interesting
things squirreled away there&hellip;.
</p>

<p>
<b><a name="trans">Transparency</a>.</b>
Any security-related tool is only as good as its design
and implementation.  <em>Transparency</em> means that, in
essence, all the moving parts are visible so you can judge
for yourself whether the tool merits your confidence.  In
the case of a program, this means that source code must
be available, and that you can verify that the program
you're running corresponds to the source code provided.

</p>

<p>
The very nature of JavaScript achieves this transparency.
The program is embedded into this actual Web page; to
examine it you need only use your browser's &ldquo;View Source&rdquo;
facility, or save the page into a file on your computer
and read it with a text editor.  JavaScript's being
an interpreted language eliminates the risk of your running
a program different from the purported source code: with
an interpreted language what you read is what you run.
</p>

<p>
Transparency is important even if you don't know enough about
programming or security to determine whether the program
contains any flaws.  The very fact that it can be examined
by anybody allows those with the required expertise to pass
judgment, and you can form your own conclusions based on
their analysis.
</p>

<h2>Credits</h2>

<p>

The pseudorandom sequence generator is based on L'Ecuyer's
two-sequence generator as described in
<cite>Communications of the ACM</cite>, Vol. 31 (1968), page 742.
A Bays-Durham shuffle is used to guard against regularities
lurking in L'Ecuyer's algorithm; see
<cite>ACM Transactions on Mathematical Software</cite>, Vol. 2 (1976)
pages 59&ndash;64 for details.
</p>

<p>
The JavaScript implementation of the
<a href="http://www.ietf.org/rfc/rfc1321.txt"><b>MD5 message-digest algorithm</b></a>
was developed by Henri Torgemane; please view the source code of this
page to examine the code, including the copyright notice and
conditions of use.  The MD5 algorithm was developed by Ron Rivest.
</p>

<p />

<hr />

<p />

<table class="r">
<tr><td align="center">
    <a class="i" href="http://validator.w3.org/check?uri=referer"><img
       class="button"
       src="valid-xhtml10.png"
       alt="Valid XHTML 1.0" height="31" width="88" /></a>
</td></tr>
</table>

<address>
by <a href="/">John Walker</a><br />
May 26, 1997<br />

Updated: November 2006
</address>

<p class="centre">
<em>This document is in the public domain.</em>
</p>
</body>
</html>