js版RSA演算法

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// RSA, a suite of routines for performing RSA public-key computations in
// JavaScript.
//
// Requires BigInt.js and Barrett.js.
//
// Copyright 1998-2005 David Shapiro.
//
// You may use, re-use, abuse, copy, and modify this code to your liking, but
// please keep this header.
//
// Thanks!
//
// Dave Shapiro
// [email protected]

function RSAKeyPair(encryptionExponent, decryptionExponent, modulus)
{
this.e = biFromHex(encryptionExponent);
this.d = biFromHex(decryptionExponent);
this.m = biFromHex(modulus);
// We can do two bytes per digit, so
// chunkSize = 2 * (number of digits in modulus - 1).
// Since biHighIndex returns the high index, not the number of digits, 1 has
// already been subtracted.
this.chunkSize = 2 * biHighIndex(this.m);
this.radix = 16;
this.barrett = new BarrettMu(this.m);
}

function twoDigit(n)
{
return (n < 10 ? "0" : "") + String(n);
}

function encryptedString(key, s)
// Altered by Rob Saunders ([email protected]). New routine pads the
// string after it has been converted to an array. This fixes an
// incompatibility with Flash MX‘s ActionScript.
{
var a = new Array();
var sl = s.length;
var i = 0;
while (i < sl) {
a[i] = s.charCodeAt(i);
i++;
}

while (a.length % key.chunkSize != 0) {
a[i++] = 0;
}

var al = a.length;
var result = "";
var j, k, block;
for (i = 0; i < al; i += key.chunkSize) {
block = new BigInt();
j = 0;
for (k = i; k < i + key.chunkSize; ++j) {
block.digits[j] = a[k++];
block.digits[j] += a[k++] << 8;
}
var crypt = key.barrett.powMod(block, key.e);
var text = key.radix == 16 ? biToHex(crypt) : biToString(crypt, key.radix);
result += text + " ";
}
return result.substring(0, result.length - 1); // Remove last space.
}

function decryptedString(key, s)
{
var blocks = s.split(" ");
var result = "";
var i, j, block;
for (i = 0; i < blocks.length; ++i) {
var bi;
if (key.radix == 16) {
bi = biFromHex(blocks[i]);
}
else {
bi = biFromString(blocks[i], key.radix);
}
block = key.barrett.powMod(bi, key.d);
for (j = 0; j <= biHighIndex(block); ++j) {
result += String.fromCharCode(block.digits[j] & 255,
block.digits[j] >> 8);
}
}
// Remove trailing null, if any.
if (result.charCodeAt(result.length - 1) == 0) {
result = result.substring(0, result.length - 1);
}
return result;
}

js版RSA演算法