RSA公钥加密算法是1977年由Ron Rivest、Adi Shamirh和LenAdleman在（美国麻省理工学院）开发的。RSA取名来自开发他们三者的名字。RSA是目前最有影响力的公钥加密算法，它能够抵抗到目前为止已知的所有密码攻击，已被ISO推荐为公钥数据加密标准。RSA算法基于一个十分简单的数论事实：将两个大素数相乘十分容易，但那时想要对其乘积进行因式分解却极其困难，因此可以将乘积公开作为加密密钥。
RSA公开密钥密码体制。所谓的公开密钥密码体制就是使用不同的加密密钥与解密密钥，是一种“由已知加密密钥推导出解密密钥在计算上是不可行的”密码体制。
在公开密钥密码体制中，加密密钥（即公开密钥）PK是公开信息，而解密密钥（即秘密密钥）SK是需要保密的。加密算法E和解密算法D也都是公开的。虽然秘密密钥SK是由公开密钥PK决定的，但却不能根据PK计算出SK。正是基于这种理论，1978年出现了著名的RSA算法，它通常是先生成一对RSA 密钥，其中之一是保密密钥，由用户保存；另一个为公开密钥，可对外公开，甚至可在网络服务器中注册。为提高保密强度，RSA密钥至少为500位长，一般推荐使用1024位。这就使加密的计算量很大。为减少计算量，在传送信息时，常采用传统加密方法与公开密钥加密方法相结合的方式，即信息采用改进的DES或IDEA对话密钥加密，然后使用RSA密钥加密对话密钥和信息摘要。对方收到信息后，用不同的密钥解密并可核对信息摘要。
RSA算法是第一个能同时用于加密和数字签名的算法，也易于理解和操作。RSA是被研究得最广泛的公钥算法，从提出到现今的三十多年里，经历了各种攻击的考验，逐渐为人们接受，普遍认为是目前最优秀的公钥方案之一。
RSA的算法涉及三个参数，n、e1、e2。其中，n是两个大质数p、q的积，n的二进制表示时所占用的位数，就是所谓的密钥长度。e1和e2是一对相关的值，e1可以任意取，
要求e1与(p-1）*(q-1）互质；
再选择e2，要求（e2*e1）mod((p-1）*(q-1））=1。
（n，e1）,(n，e2）就是密钥对。其中(n，e1）为公钥，(n，e2）为私钥。
RSA加解密的算法完全相同，设A为明文，B为密文，则：
A=B^e2 mod n；
B=A^e1 mod n；
公钥加密体制中，一般用公钥加密，私钥解密
e1和e2可以互换使用，即：
A=B^e1 mod n；
B=A^e2 mod n;
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JAVAEE项目中很多时候都需要对核心数据进行加密传输，采用非对称加密算法在前段对数据进行加密，在服务端进行解密是一个不错的方式。而常用的实现是采用RSA非对称加密方法。具体步骤为：
1、在服务端用密码种子生成密钥对，保存密码种子（一个特定的密码种子，生成特定的密钥对，密码种子确定，密钥对确定）或者直接保存私钥
2、把公钥传到页面
3、页面用JS根据公钥把需要加密的数据进行加密，把加密后的数据传回服务端
4、服务端取出保存的密码种子或者直接保存的私钥，采用私钥对加密字符串进行解密，得到明文
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RSA.java(服务端代码)
注意：需要bouncycastle.jar
-------------------------------------------------------------------------------------------------------------------------------
package org.common.util;
import java.security.InvalidParameterException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Provider;
import java.security.SecureRandom;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import javax.crypto.Cipher;
import org.apache.commons.lang3.StringUtils;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.encoders.Hex;
/**
* RSA算法加密/解密工具类。
*
* @author Administrator
*
*/
public class RSA {
/** 算法名称 */
private static final String ALGORITHOM = "RSA";
/** 密钥大小 */
private static final int KEY_SIZE = 1024;
/** 默认的安全服务提供者 */
private static final Provider DEFAULT_PROVIDER = new BouncyCastleProvider();
private static KeyPairGenerator keyPairGen = null;
private static KeyFactory keyFactory = null;
/** 缓存的密钥对。 */
private static KeyPair oneKeyPair = null;
private static String radamKey = "";
static {
try {
keyPairGen = KeyPairGenerator.getInstance(ALGORITHOM,
DEFAULT_PROVIDER);
keyFactory = KeyFactory.getInstance(ALGORITHOM, DEFAULT_PROVIDER);
} catch (NoSuchAlgorithmException ex) {
ex.printStackTrace();
}
}
/**
* 生成并返回RSA密钥对。
*/
private static synchronized KeyPair generateKeyPair() {
try {
keyPairGen.initialize(KEY_SIZE,
new SecureRandom(radamKey.getBytes()));
oneKeyPair = keyPairGen.generateKeyPair();
return oneKeyPair;
} catch (InvalidParameterException ex) {
ex.printStackTrace();
} catch (NullPointerException ex) {
ex.printStackTrace();
}
return null;
}
/** 返回已初始化的默认的公钥。 */
public static RSAPublicKey getDefaultPublicKey() {
KeyPair keyPair = generateKeyPair();
if (keyPair != null) {
return (RSAPublicKey) keyPair.getPublic();
}
return null;
}
/**
* 使用指定的私钥解密数据。
*
* @param privateKey 给定的私钥。
* @param data 要解密的数据。
* @return 原数据。
*/
public static byte[] decrypt(PrivateKey privateKey, byte[] data) throws Exception {
Cipher ci = Cipher.getInstance(ALGORITHOM, DEFAULT_PROVIDER);
ci.init(Cipher.DECRYPT_MODE, privateKey);
return ci.doFinal(data);
}
/**
* 使用默认的私钥解密给定的字符串。
* <p />
* 若{@code encrypttext} 为 {@code null}或空字符串则返回 {@code null}。
* 私钥不匹配时，返回 {@code null}。
*
* @param encrypttext 密文。
* @return 原文字符串。
*/
public static String decryptString(String encrypttext) {
if(StringUtils.isBlank(encrypttext)) {
return null;
}
KeyPair keyPair = generateKeyPair();
try {
byte[] en_data = Hex.decode(encrypttext);
byte[] data = decrypt((RSAPrivateKey)keyPair.getPrivate(), en_data);
return new String(data);
} catch(NullPointerException ex) {
ex.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
/**
* 使用默认的私钥解密由JS加密（使用此类提供的公钥加密）的字符串。
*
* @param encrypttext 密文。
* @return {@code encrypttext} 的原文字符串。
*/
public static String decryptStringByJs(String encrypttext) {
String text = decryptString(encrypttext);
if(text == null) {
return null;
}
return StringUtils.reverse(text);
}
public static void main(String[] args) {
//密码种子，一个密码种子生产一组RSA密码
RSA.radamKey = "1111";
//获取公钥，分发公钥（e1,n）
RSAPublicKey publicKey = RSA.getDefaultPublicKey();
//公钥-系数(n)
System.out.println("public key modulus:"
+ new String(Hex.encode(publicKey.getModulus().toByteArray())));
//公钥-指数(e1)
System.out.println("public key exponent:"
+ new String(Hex.encode(publicKey.getPublicExponent()
.toByteArray())));
//JS加密后的字符串
String pppp = "6e269bdf7f7670ffaff669d86d93e63fd91f2d6dd4f7e57ca58c614de65c0828e608bdd0f3e81d3630f8533f5286e0f55caa005ebe6d3faf3b9cc130d9ecff51d1f77eeed48156431cbf5de62cf6899084a4e92890827edbebbf506ecbb022de4a0e3131f2ffefe3368c7b7f929362edb4af419b837456c275f643a5c760a4ff";
//解密后的字符串
String kkkk = RSA.decryptStringByJs(pppp);
System.out.println("解密后文字：" + kkkk);
}
}
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html页面代码
注意：security.js工具库、jquery支持
-------------------------------------------------------------------------------------------------------------------------------
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>JavaScript RSA Encryption Demo</title>
</head>
<script language="JavaScript" type="text/javascript" src="security.js"></script>
<script language="JavaScript" type="text/javascript" src="jquery-git1.js"></script>
<script language="JavaScript">
<!--
function encry()
{
var modulus = $('#hid_modulus').val(), exponent = $('#hid_exponent').val();
var key = RSAUtils.getKeyPair(exponent, '', modulus);
var word =$("#word").val();
var apwd1 = RSAUtils.encryptedString(key, word);
$("#clj").text(apwd1);
}
//-->
</script>
<body onLoad='set_1024f4();' onClick='rng_seed_time();' onKeyPress='rng_seed_time();'>
<h1>JavaScript RSA Encryption Demo</h1>
需要加密的字符串：
<input type="text" id="word" value="test"/>
<br/>
<input type="text" id="hid_modulus" value="00c99f8aab91bccb525d6ea16c40a8eb31dfa9594d1b487167a96d24c8e2d48ed1e9d759f3d1425728016cfffb9b42311108dc6b1f749e6902d6bc072d0533adc489e87eecd980590460fe62290b6a6210e5584919bf85a9cb7b02ebb3ef89aa0a61120dc3cfac1af480905bf269890654cc94e44512b2adc2bb6054cd15971061"/>
<br/>
<input type="text" id="hid_exponent" value="010001"/>
<input type="button" onclick="encry()" value="加密"/>
<div id="clj"></div>
</body>
</html>
-------------------------------------------------------------------------------------------------------------------------------
security.js源码
-------------------------------------------------------------------------------------------------------------------------------
/*
* RSA, a suite of routines for performing RSA public-key computations in JavaScript.
* Copyright 1998-2005 David Shapiro.
* Dave Shapiro
* dave@ohdave.com
* changed by Fuchun, 2010-05-06
* fcrpg2005@gmail.com
*/
(function($w) {
if(typeof $w.RSAUtils === 'undefined')
var RSAUtils = $w.RSAUtils = {};
var biRadixBase = 2;
var biRadixBits = 16;
var bitsPerDigit = biRadixBits;
var biRadix = 1 << 16; // = 2^16 = 65536
var biHalfRadix = biRadix >>> 1;
var biRadixSquared = biRadix * biRadix;
var maxDigitVal = biRadix - 1;
var maxInteger = 9999999999999998;
//maxDigits:
//Change this to accommodate your largest number size. Use setMaxDigits()
//to change it!
//
//In general, if you're working with numbers of size N bits, you'll need 2*N
//bits of storage. Each digit holds 16 bits. So, a 1024-bit key will need
//
//1024 * 2 / 16 = 128 digits of storage.
//
var maxDigits;
var ZERO_ARRAY;
var bigZero, bigOne;
var BigInt = $w.BigInt = function(flag) {
if (typeof flag == "boolean" && flag == true) {
this.digits = null;
} else {
this.digits = ZERO_ARRAY.slice(0);
}
this.isNeg = false;
};
RSAUtils.setMaxDigits = function(value) {
maxDigits = value;
ZERO_ARRAY = new Array(maxDigits);
for (var iza = 0; iza < ZERO_ARRAY.length; iza++) ZERO_ARRAY[iza] = 0;
bigZero = new BigInt();
bigOne = new BigInt();
bigOne.digits[0] = 1;
};
RSAUtils.setMaxDigits(20);
//The maximum number of digits in base 10 you can convert to an
//integer without JavaScript throwing up on you.
var dpl10 = 15;
RSAUtils.biFromNumber = function(i) {
var result = new BigInt();
result.isNeg = i < 0;
i = Math.abs(i);
var j = 0;
while (i > 0) {
result.digits[j++] = i & maxDigitVal;
i = Math.floor(i / biRadix);
}
return result;
};
//lr10 = 10 ^ dpl10
var lr10 = RSAUtils.biFromNumber(1000000000000000);
RSAUtils.biFromDecimal = function(s) {
var isNeg = s.charAt(0) == '-';
var i = isNeg ? 1 : 0;
var result;
// Skip leading zeros.
while (i < s.length && s.charAt(i) == '0') ++i;
if (i == s.length) {
result = new BigInt();
}
else {
var digitCount = s.length - i;
var fgl = digitCount % dpl10;
if (fgl == 0) fgl = dpl10;
result = RSAUtils.biFromNumber(Number(s.substr(i, fgl)));
i += fgl;
while (i < s.length) {
result = RSAUtils.biAdd(RSAUtils.biMultiply(result, lr10),
RSAUtils.biFromNumber(Number(s.substr(i, dpl10))));
i += dpl10;
}
result.isNeg = isNeg;
}
return result;
};
RSAUtils.biCopy = function(bi) {
var result = new BigInt(true);
result.digits = bi.digits.slice(0);
result.isNeg = bi.isNeg;
return result;
};
RSAUtils.reverseStr = function(s) {
var result = "";
for (var i = s.length - 1; i > -1; --i) {
result += s.charAt(i);
}
return result;
};
var hexatrigesimalToChar = [
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y', 'z'
];
RSAUtils.biToString = function(x, radix) { // 2 <= radix <= 36
var b = new BigInt();
b.digits[0] = radix;
var qr = RSAUtils.biDivideModulo(x, b);
var result = hexatrigesimalToChar[qr[1].digits[0]];
while (RSAUtils.biCompare(qr[0], bigZero) == 1) {
qr = RSAUtils.biDivideModulo(qr[0], b);
digit = qr[1].digits[0];
result += hexatrigesimalToChar[qr[1].digits[0]];
}
return (x.isNeg ? "-" : "") + RSAUtils.reverseStr(result);
};
RSAUtils.biToDecimal = function(x) {
var b = new BigInt();
b.digits[0] = 10;
var qr = RSAUtils.biDivideModulo(x, b);
var result = String(qr[1].digits[0]);
while (RSAUtils.biCompare(qr[0], bigZero) == 1) {
qr = RSAUtils.biDivideModulo(qr[0], b);
result += String(qr[1].digits[0]);
}
return (x.isNeg ? "-" : "") + RSAUtils.reverseStr(result);
};
var hexToChar = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'a', 'b', 'c', 'd', 'e', 'f'];
RSAUtils.digitToHex = function(n) {
var mask = 0xf;
var result = "";
for (i = 0; i < 4; ++i) {
result += hexToChar[n & mask];
n >>>= 4;
}
return RSAUtils.reverseStr(result);
};
RSAUtils.biToHex = function(x) {
var result = "";
var n = RSAUtils.biHighIndex(x);
for (var i = RSAUtils.biHighIndex(x); i > -1; --i) {
result += RSAUtils.digitToHex(x.digits[i]);
}
return result;
};
RSAUtils.charToHex = function(c) {
var ZERO = 48;
var NINE = ZERO + 9;
var littleA = 97;
var littleZ = littleA + 25;
var bigA = 65;
var bigZ = 65 + 25;
var result;
if (c >= ZERO && c <= NINE) {
result = c - ZERO;
} else if (c >= bigA && c <= bigZ) {
result = 10 + c - bigA;
} else if (c >= littleA && c <= littleZ) {
result = 10 + c - littleA;
} else {
result = 0;
}
return result;
};
RSAUtils.hexToDigit = function(s) {
var result = 0;
var sl = Math.min(s.length, 4);
for (var i = 0; i < sl; ++i) {
result <<= 4;
result |= RSAUtils.charToHex(s.charCodeAt(i));
}
return result;
};
RSAUtils.biFromHex = function(s) {
var result = new BigInt();
var sl = s.length;
for (var i = sl, j = 0; i > 0; i -= 4, ++j) {
result.digits[j] = RSAUtils.hexToDigit(s.substr(Math.max(i - 4, 0), Math.min(i, 4)));
}
return result;
};
RSAUtils.biFromString = function(s, radix) {
var isNeg = s.charAt(0) == '-';
var istop = isNeg ? 1 : 0;
var result = new BigInt();
var place = new BigInt();
place.digits[0] = 1; // radix^0
for (var i = s.length - 1; i >= istop; i--) {
var c = s.charCodeAt(i);
var digit = RSAUtils.charToHex(c);
var biDigit = RSAUtils.biMultiplyDigit(place, digit);
result = RSAUtils.biAdd(result, biDigit);
place = RSAUtils.biMultiplyDigit(place, radix);
}
result.isNeg = isNeg;
return result;
};
RSAUtils.biDump = function(b) {
return (b.isNeg ? "-" : "") + b.digits.join(" ");
};
RSAUtils.biAdd = function(x, y) {
var result;
if (x.isNeg != y.isNeg) {
y.isNeg = !y.isNeg;
result = RSAUtils.biSubtract(x, y);
y.isNeg = !y.isNeg;
}
else {
result = new BigInt();
var c = 0;
var n;
for (var i = 0; i < x.digits.length; ++i) {
n = x.digits[i] + y.digits[i] + c;
result.digits[i] = n % biRadix;
c = Number(n >= biRadix);
}
result.isNeg = x.isNeg;
}
return result;
};
RSAUtils.biSubtract = function(x, y) {
var result;
if (x.isNeg != y.isNeg) {
y.isNeg = !y.isNeg;
result = RSAUtils.biAdd(x, y);
y.isNeg = !y.isNeg;
} else {
result = new BigInt();
var n, c;
c = 0;
for (var i = 0; i < x.digits.length; ++i) {
n = x.digits[i] - y.digits[i] + c;
result.digits[i] = n % biRadix;
// Stupid non-conforming modulus operation.
if (result.digits[i] < 0) result.digits[i] += biRadix;
c = 0 - Number(n < 0);
}
// Fix up the negative sign, if any.
if (c == -1) {
c = 0;
for (var i = 0; i < x.digits.length; ++i) {
n = 0 - result.digits[i] + c;
result.digits[i] = n % biRadix;
// Stupid non-conforming modulus operation.
if (result.digits[i] < 0) result.digits[i] += biRadix;
c = 0 - Number(n < 0);
}
// Result is opposite sign of arguments.
result.isNeg = !x.isNeg;
} else {
// Result is same sign.
result.isNeg = x.isNeg;
}
}
return result;
};
RSAUtils.biHighIndex = function(x) {
var result = x.digits.length - 1;
while (result > 0 && x.digits[result] == 0) --result;
return result;
};
RSAUtils.biNumBits = function(x) {
var n = RSAUtils.biHighIndex(x);
var d = x.digits[n];
var m = (n + 1) * bitsPerDigit;
var result;
for (result = m; result > m - bitsPerDigit; --result) {
if ((d & 0x8000) != 0) break;
d <<= 1;
}
return result;
};
RSAUtils.biMultiply = function(x, y) {
var result = new BigInt();
var c;
var n = RSAUtils.biHighIndex(x);
var t = RSAUtils.biHighIndex(y);
var u, uv, k;
for (var i = 0; i <= t; ++i) {
c = 0;
k = i;
for (j = 0; j <= n; ++j, ++k) {
uv = result.digits[k] + x.digits[j] * y.digits[i] + c;
result.digits[k] = uv & maxDigitVal;
c = uv >>> biRadixBits;
//c = Math.floor(uv / biRadix);
}
result.digits[i + n + 1] = c;
}
// Someone give me a logical xor, please.
result.isNeg = x.isNeg != y.isNeg;
return result;
};
RSAUtils.biMultiplyDigit = function(x, y) {
var n, c, uv;
result = new BigInt();
n = RSAUtils.biHighIndex(x);
c = 0;
for (var j = 0; j <= n; ++j) {
uv = result.digits[j] + x.digits[j] * y + c;
result.digits[j] = uv & maxDigitVal;
c = uv >>> biRadixBits;
//c = Math.floor(uv / biRadix);
}
result.digits[1 + n] = c;
return result;
};
RSAUtils.arrayCopy = function(src, srcStart, dest, destStart, n) {
var m = Math.min(srcStart + n, src.length);
for (var i = srcStart, j = destStart; i < m; ++i, ++j) {
dest[j] = src[i];
}
};
var highBitMasks = [0x0000, 0x8000, 0xC000, 0xE000, 0xF000, 0xF800,
0xFC00, 0xFE00, 0xFF00, 0xFF80, 0xFFC0, 0xFFE0,
0xFFF0, 0xFFF8, 0xFFFC, 0xFFFE, 0xFFFF];
RSAUtils.biShiftLeft = function(x, n) {
var digitCount = Math.floor(n / bitsPerDigit);
var result = new BigInt();
RSAUtils.arrayCopy(x.digits, 0, result.digits, digitCount,
result.digits.length - digitCount);
var bits = n % bitsPerDigit;
var rightBits = bitsPerDigit - bits;
for (var i = result.digits.length - 1, i1 = i - 1; i > 0; --i, --i1) {
result.digits[i] = ((result.digits[i] << bits) & maxDigitVal) |
((result.digits[i1] & highBitMasks[bits]) >>>
(rightBits));
}
result.digits[0] = ((result.digits[i] << bits) & maxDigitVal);
result.isNeg = x.isNeg;
return result;
};
var lowBitMasks = [0x0000, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F,
0x003F, 0x007F, 0x00FF, 0x01FF, 0x03FF, 0x07FF,
0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF];
RSAUtils.biShiftRight = function(x, n) {
var digitCount = Math.floor(n / bitsPerDigit);
var result = new BigInt();
RSAUtils.arrayCopy(x.digits, digitCount, result.digits, 0,
x.digits.length - digitCount);
var bits = n % bitsPerDigit;
var leftBits = bitsPerDigit - bits;
for (var i = 0, i1 = i + 1; i < result.digits.length - 1; ++i, ++i1) {
result.digits[i] = (result.digits[i] >>> bits) |
((result.digits[i1] & lowBitMasks[bits]) << leftBits);
}
result.digits[result.digits.length - 1] >>>= bits;
result.isNeg = x.isNeg;
return result;
};
RSAUtils.biMultiplyByRadixPower = function(x, n) {
var result = new BigInt();
RSAUtils.arrayCopy(x.digits, 0, result.digits, n, result.digits.length - n);
return result;
};
RSAUtils.biDivideByRadixPower = function(x, n) {
var result = new BigInt();
RSAUtils.arrayCopy(x.digits, n, result.digits, 0, result.digits.length - n);
return result;
};
RSAUtils.biModuloByRadixPower = function(x, n) {
var result = new BigInt();
RSAUtils.arrayCopy(x.digits, 0, result.digits, 0, n);
return result;
};
RSAUtils.biCompare = function(x, y) {
if (x.isNeg != y.isNeg) {
return 1 - 2 * Number(x.isNeg);
}
for (var i = x.digits.length - 1; i >= 0; --i) {
if (x.digits[i] != y.digits[i]) {
if (x.isNeg) {
return 1 - 2 * Number(x.digits[i] > y.digits[i]);
} else {
return 1 - 2 * Number(x.digits[i] < y.digits[i]);
}
}
}
return 0;
};
RSAUtils.biDivideModulo = function(x, y) {
var nb = RSAUtils.biNumBits(x);
var tb = RSAUtils.biNumBits(y);
var origYIsNeg = y.isNeg;
var q, r;
if (nb < tb) {
// |x| < |y|
if (x.isNeg) {
q = RSAUtils.biCopy(bigOne);
q.isNeg = !y.isNeg;
x.isNeg = false;
y.isNeg = false;
r = biSubtract(y, x);
// Restore signs, 'cause they're references.
x.isNeg = true;
y.isNeg = origYIsNeg;
} else {
q = new BigInt();
r = RSAUtils.biCopy(x);
}
return [q, r];
}
q = new BigInt();
r = x;
// Normalize Y.
var t = Math.ceil(tb / bitsPerDigit) - 1;
var lambda = 0;
while (y.digits[t] < biHalfRadix) {
y = RSAUtils.biShiftLeft(y, 1);
++lambda;
++tb;
t = Math.ceil(tb / bitsPerDigit) - 1;
}
// Shift r over to keep the quotient constant. We'll shift the
// remainder back at the end.
r = RSAUtils.biShiftLeft(r, lambda);
nb += lambda; // Update the bit count for x.
var n = Math.ceil(nb / bitsPerDigit) - 1;
var b = RSAUtils.biMultiplyByRadixPower(y, n - t);
while (RSAUtils.biCompare(r, b) != -1) {
++q.digits[n - t];
r = RSAUtils.biSubtract(r, b);
}
for (var i = n; i > t; --i) {
var ri = (i >= r.digits.length) ? 0 : r.digits[i];
var ri1 = (i - 1 >= r.digits.length) ? 0 : r.digits[i - 1];
var ri2 = (i - 2 >= r.digits.length) ? 0 : r.digits[i - 2];
var yt = (t >= y.digits.length) ? 0 : y.digits[t];
var yt1 = (t - 1 >= y.digits.length) ? 0 : y.digits[t - 1];
if (ri == yt) {
q.digits[i - t - 1] = maxDigitVal;
} else {
q.digits[i - t - 1] = Math.floor((ri * biRadix + ri1) / yt);
}
var c1 = q.digits[i - t - 1] * ((yt * biRadix) + yt1);
var c2 = (ri * biRadixSquared) + ((ri1 * biRadix) + ri2);
while (c1 > c2) {
--q.digits[i - t - 1];
c1 = q.digits[i - t - 1] * ((yt * biRadix) | yt1);
c2 = (ri * biRadix * biRadix) + ((ri1 * biRadix) + ri2);
}
b = RSAUtils.biMultiplyByRadixPower(y, i - t - 1);
r = RSAUtils.biSubtract(r, RSAUtils.biMultiplyDigit(b, q.digits[i - t - 1]));
if (r.isNeg) {
r = RSAUtils.biAdd(r, b);
--q.digits[i - t - 1];
}
}
r = RSAUtils.biShiftRight(r, lambda);
// Fiddle with the signs and stuff to make sure that 0 <= r < y.
q.isNeg = x.isNeg != origYIsNeg;
if (x.isNeg) {
if (origYIsNeg) {
q = RSAUtils.biAdd(q, bigOne);
} else {
q = RSAUtils.biSubtract(q, bigOne);
}
y = RSAUtils.biShiftRight(y, lambda);
r = RSAUtils.biSubtract(y, r);
}
// Check for the unbelievably stupid degenerate case of r == -0.
if (r.digits[0] == 0 && RSAUtils.biHighIndex(r) == 0) r.isNeg = false;
return [q, r];
};
RSAUtils.biDivide = function(x, y) {
return RSAUtils.biDivideModulo(x, y)[0];
};
RSAUtils.biModulo = function(x, y) {
return RSAUtils.biDivideModulo(x, y)[1];
};
RSAUtils.biMultiplyMod = function(x, y, m) {
return RSAUtils.biModulo(RSAUtils.biMultiply(x, y), m);
};
RSAUtils.biPow = function(x, y) {
var result = bigOne;
var a = x;
while (true) {
if ((y & 1) != 0) result = RSAUtils.biMultiply(result, a);
y >>= 1;
if (y == 0) break;
a = RSAUtils.biMultiply(a, a);
}
return result;
};
RSAUtils.biPowMod = function(x, y, m) {
var result = bigOne;
var a = x;
var k = y;
while (true) {
if ((k.digits[0] & 1) != 0) result = RSAUtils.biMultiplyMod(result, a, m);
k = RSAUtils.biShiftRight(k, 1);
if (k.digits[0] == 0 && RSAUtils.biHighIndex(k) == 0) break;
a = RSAUtils.biMultiplyMod(a, a, m);
}
return result;
};
$w.BarrettMu = function(m) {
this.modulus = RSAUtils.biCopy(m);
this.k = RSAUtils.biHighIndex(this.modulus) + 1;
var b2k = new BigInt();
b2k.digits[2 * this.k] = 1; // b2k = b^(2k)
this.mu = RSAUtils.biDivide(b2k, this.modulus);
this.bkplus1 = new BigInt();
this.bkplus1.digits[this.k + 1] = 1; // bkplus1 = b^(k+1)
this.modulo = BarrettMu_modulo;
this.multiplyMod = BarrettMu_multiplyMod;
this.powMod = BarrettMu_powMod;
};
function BarrettMu_modulo(x) {
var $dmath = RSAUtils;
var q1 = $dmath.biDivideByRadixPower(x, this.k - 1);
var q2 = $dmath.biMultiply(q1, this.mu);
var q3 = $dmath.biDivideByRadixPower(q2, this.k + 1);
var r1 = $dmath.biModuloByRadixPower(x, this.k + 1);
var r2term = $dmath.biMultiply(q3, this.modulus);
var r2 = $dmath.biModuloByRadixPower(r2term, this.k + 1);
var r = $dmath.biSubtract(r1, r2);
if (r.isNeg) {
r = $dmath.biAdd(r, this.bkplus1);
}
var rgtem = $dmath.biCompare(r, this.modulus) >= 0;
while (rgtem) {
r = $dmath.biSubtract(r, this.modulus);
rgtem = $dmath.biCompare(r, this.modulus) >= 0;
}
return r;
}
function BarrettMu_multiplyMod(x, y) {
/*
x = this.modulo(x);
y = this.modulo(y);
*/
var xy = RSAUtils.biMultiply(x, y);
return this.modulo(xy);
}
function BarrettMu_powMod(x, y) {
var result = new BigInt();
result.digits[0] = 1;
var a = x;
var k = y;
while (true) {
if ((k.digits[0] & 1) != 0) result = this.multiplyMod(result, a);
k = RSAUtils.biShiftRight(k, 1);
if (k.digits[0] == 0 && RSAUtils.biHighIndex(k) == 0) break;
a = this.multiplyMod(a, a);
}
return result;
}
var RSAKeyPair = function(encryptionExponent, decryptionExponent, modulus) {
var $dmath = RSAUtils;
this.e = $dmath.biFromHex(encryptionExponent);
this.d = $dmath.biFromHex(decryptionExponent);
this.m = $dmath.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 * $dmath.biHighIndex(this.m);
this.radix = 16;
this.barrett = new $w.BarrettMu(this.m);
};
RSAUtils.getKeyPair = function(encryptionExponent, decryptionExponent, modulus) {
return new RSAKeyPair(encryptionExponent, decryptionExponent, modulus);
};
if(typeof $w.twoDigit === 'undefined') {
$w.twoDigit = function(n) {
return (n < 10 ? "0" : "") + String(n);
};
}
// Altered by Rob Saunders (rob@robsaunders.net). New routine pads the
// string after it has been converted to an array. This fixes an
// incompatibility with Flash MX's ActionScript.
RSAUtils.encryptedString = function(key, s) {
var a = [];
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 ? RSAUtils.biToHex(crypt) : RSAUtils.biToString(crypt, key.radix);
result += text + " ";
}
return result.substring(0, result.length - 1); // Remove last space.
};
RSAUtils.decryptedString = function(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 = RSAUtils.biFromHex(blocks[i]);
}
else {
bi = RSAUtils.biFromString(blocks[i], key.radix);
}
block = key.barrett.powMod(bi, key.d);
for (j = 0; j <= RSAUtils.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;
};
RSAUtils.setMaxDigits(130);
})(window);
