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<h1 class="page-title">Source: crypto/random.js</h1>
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<pre class="prettyprint source"><code>// GPG4Browsers - An OpenPGP implementation in javascript
// Copyright (C) 2011 Recurity Labs GmbH
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
// The GPG4Browsers crypto interface
/**
* @requires type/mpi
* @module crypto/random
*/
var type_mpi = require('../type/mpi.js');
var nodeCrypto = null;
if (typeof window === 'undefined') {
nodeCrypto = require('crypto');
}
module.exports = {
/**
* Retrieve secure random byte string of the specified length
* @param {Integer} length Length in bytes to generate
* @return {String} Random byte string
*/
getRandomBytes: function(length) {
var result = '';
for (var i = 0; i < length; i++) {
result += String.fromCharCode(this.getSecureRandomOctet());
}
return result;
},
/**
* Return a pseudo-random number in the specified range
* @param {Integer} from Min of the random number
* @param {Integer} to Max of the random number (max 32bit)
* @return {Integer} A pseudo random number
*/
getPseudoRandom: function(from, to) {
return Math.round(Math.random() * (to - from)) + from;
},
/**
* Return a secure random number in the specified range
* @param {Integer} from Min of the random number
* @param {Integer} to Max of the random number (max 32bit)
* @return {Integer} A secure random number
*/
getSecureRandom: function(from, to) {
var randUint = this.getSecureRandomUint();
var bits = ((to - from)).toString(2).length;
while ((randUint & (Math.pow(2, bits) - 1)) > (to - from)) {
randUint = this.getSecureRandomUint();
}
return from + (Math.abs(randUint & (Math.pow(2, bits) - 1)));
},
getSecureRandomOctet: function() {
var buf = new Uint8Array(1);
this.getRandomValues(buf);
return buf[0];
},
getSecureRandomUint: function() {
var buf = new Uint8Array(4);
var dv = new DataView(buf.buffer);
this.getRandomValues(buf);
return dv.getUint32(0);
},
/**
* Helper routine which calls platform specific crypto random generator
* @param {Uint8Array} buf
*/
getRandomValues: function(buf) {
if (typeof window !== 'undefined' && window.crypto) {
window.crypto.getRandomValues(buf);
} else if (nodeCrypto) {
var bytes = nodeCrypto.randomBytes(buf.length);
buf.set(bytes);
} else if (this.randomBuffer.buffer) {
this.randomBuffer.get(buf);
} else {
throw new Error('No secure random number generator available.');
}
},
/**
* Create a secure random big integer of bits length
* @param {Integer} bits Bit length of the MPI to create
* @return {BigInteger} Resulting big integer
*/
getRandomBigInteger: function(bits) {
if (bits < 0) {
return null;
}
var numBytes = Math.floor((bits + 7) / 8);
var randomBits = this.getRandomBytes(numBytes);
if (bits % 8 > 0) {
randomBits = String.fromCharCode(
(Math.pow(2, bits % 8) - 1) &
randomBits.charCodeAt(0)) +
randomBits.substring(1);
}
var mpi = new type_mpi();
mpi.fromBytes(randomBits);
return mpi.toBigInteger();
},
getRandomBigIntegerInRange: function(min, max) {
if (max.compareTo(min) <= 0) {
return;
}
var range = max.subtract(min);
var r = this.getRandomBigInteger(range.bitLength());
while (r > range) {
r = this.getRandomBigInteger(range.bitLength());
}
return min.add(r);
},
randomBuffer: new RandomBuffer()
};
/**
* Buffer for secure random numbers
*/
function RandomBuffer() {
this.buffer = null;
this.size = null;
}
/**
* Initialize buffer
* @param {Integer} size size of buffer
*/
RandomBuffer.prototype.init = function(size) {
this.buffer = new Uint32Array(size);
this.size = 0;
};
/**
* Concat array of secure random numbers to buffer
* @param {Uint32Array} buf
*/
RandomBuffer.prototype.set = function(buf) {
if (!this.buffer) {
throw new Error('RandomBuffer is not initialized');
}
var freeSpace = this.buffer.length - this.size;
if (buf.length > freeSpace) {
buf = buf.subarray(0, freeSpace);
}
this.buffer.set(buf, this.size);
this.size += buf.length;
};
/**
* Take numbers out of buffer and copy to array
* @param {Uint32Array} buf the destination array
*/
RandomBuffer.prototype.get = function(buf) {
if (!this.buffer) {
throw new Error('RandomBuffer is not initialized');
}
if (this.size < buf.length) {
throw new Error('Random number buffer depleted.')
}
for (var i = 0; i < buf.length; i++) {
buf[i] = this.buffer[--this.size];
}
};
</code></pre>
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