JavaWeb RSA加密使用小解

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1. RSA密文和密钥

不管明文长度是多少，RSA 生成的密文长度总是固定的。
但是明文长度不能超过密钥长度。比如 Java 默认的 RSA 加密实现不允许明文长度超过密钥长度减去 11(单位是字节，也就是 byte)。也就是说，如果我们定义的密钥(我们可以通过 java.security.KeyPairGenerator.initialize(int keysize) 来定义密钥长度)长度为 1024(单位是位，也就是 bit)，生成的密钥长度就是 1024位 / 8位/字节 = 128字节，那么我们需要加密的明文长度不能超过 128字节 -
11 字节 = 117字节。也就是说，我们最大能将 117 字节长度的明文进行加密，否则会出问题(抛诸如 javax.crypto.IllegalBlockSizeException:Data must not be longer than 53 bytes 的异常)。

2. Java端

String modulus = publicKey.getModulus().toString(16);

String pubexp =publicKey.getPublicExponent().toString(16);

String priexp =privateKey.getPrivateExponent().toString(16);

注意需要使用16进制下发到客户端

package com.inphase.demo.utils;

import java.math.BigInteger;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

importjava.security.NoSuchAlgorithmException;

import java.security.Security;

importjava.security.interfaces.RSAPrivateKey;

importjava.security.interfaces.RSAPublicKey;

import java.security.spec.RSAPrivateKeySpec;

import java.security.spec.RSAPublicKeySpec;

import java.util.HashMap;

import javax.crypto.Cipher;

importorg.bouncycastle.jce.provider.BouncyCastleProvider;

public class RSAUtils {

/**

* 加密算法RSA

publicstatic final String KEY_ALGORITHM = "RSA";

/**

* 签名算法

public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

/**

* 生成公钥和私钥

* @throws NoSuchAlgorithmException

publicstatic HashMap<String, Object> getKeys()

throwsNoSuchAlgorithmException {

Security.addProvider(newBouncyCastleProvider());

HashMap<String,Object> map = new HashMap<String, Object>();

KeyPairGeneratorkeyPairGen = KeyPairGenerator.getInstance("RSA",

newBouncyCastleProvider());

keyPairGen.initialize(1024);

KeyPairkeyPair = keyPairGen.generateKeyPair();

RSAPublicKeypublicKey = (RSAPublicKey) keyPair.getPublic();

RSAPrivateKeyprivateKey = (RSAPrivateKey) keyPair.getPrivate();

map.put("public",publicKey);

map.put("private",privateKey);

returnmap;

}

/**

* 使用模和指数生成RSA公钥

* @param modulus

* 模

* @param exponent

* 指数

* @return

publicstatic RSAPublicKey getPublicKey(String modulus, String exponent) {

Security.addProvider(newBouncyCastleProvider());

try{

BigIntegerb1 = new BigInteger(modulus);

BigIntegerb2 = new BigInteger(exponent);

KeyFactorykeyFactory = KeyFactory.getInstance("RSA",

newBouncyCastleProvider());

RSAPublicKeySpeckeySpec = new RSAPublicKeySpec(b1, b2);

return(RSAPublicKey) keyFactory.generatePublic(keySpec);

}catch (Exception e) {

e.printStackTrace();

returnnull;

}

/**

* 使用模和指数生成RSA私钥 /None/NoPadding

* @param modulus

* 模

* @param exponent

* 指数

* @return

publicstatic RSAPrivateKey getPrivateKey(String modulus, String exponent) {

try{

Security.addProvider(newBouncyCastleProvider());

BigIntegerb1 = new BigInteger(modulus);

BigInteger b2 = new BigInteger(exponent);

KeyFactorykeyFactory = KeyFactory.getInstance("RSA",

newBouncyCastleProvider());

RSAPrivateKeySpeckeySpec = new RSAPrivateKeySpec(b1, b2);

return(RSAPrivateKey) keyFactory.generatePrivate(keySpec);

}catch (Exception e) {

e.printStackTrace();

returnnull;

}

/**

* 公钥加密

* @param data

* @param publicKey

* @return

* @throws Exception

publicstatic String encryptByPublicKey(String data, RSAPublicKey publicKey)

throwsException {

Security.addProvider(newBouncyCastleProvider());

Ciphercipher = Cipher.getInstance("RSA", new BouncyCastleProvider());

cipher.init(Cipher.ENCRYPT_MODE,publicKey);

//模长

intkey_len = publicKey.getModulus().bitLength() / 8;

// 加密数据长度 <= 模长-11

String[]datas = splitString(data, key_len - 11);

Stringmi = "";

//如果明文长度大于模长-11则要分组加密

for(String s : datas) {

mi+= bcd2Str(cipher.doFinal(s.getBytes()));

}

returnmi;

}

/**

* 私钥解密

* @param data

* @param privateKey

* @return

* @throws Exception

publicstatic String decryptByPrivateKey(String data,

RSAPrivateKeyprivateKey) throws Exception {

Security.addProvider(newBouncyCastleProvider());

Ciphercipher = Cipher.getInstance("RSA", new BouncyCastleProvider());

cipher.init(Cipher.DECRYPT_MODE,privateKey);

//模长

intkey_len = privateKey.getModulus().bitLength() / 8;

byte[]bytes = data.getBytes();

byte[]bcd = ASCII_To_BCD(bytes, bytes.length);

//System.err.println(bcd.length);

//如果密文长度大于模长则要分组解密

Stringming = "";

byte[][]arrays = splitArray(bcd, key_len);

try{

for(byte[] arr : arrays) {

ming+= new String(cipher.doFinal(arr));

}

}catch (Exception e) {

e.printStackTrace();

}

returnming;

}

/**

* ASCII码转BCD码

publicstatic byte[] ASCII_To_BCD(byte[] ascii, int asc_len) {

byte[]bcd = new byte[asc_len / 2];

intj = 0;

for(int i = 0; i < (asc_len + 1) / 2; i++) {

bcd[i]= asc_to_bcd(ascii[j++]);

bcd[i]= (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i]<< 4));

}

returnbcd;

}

publicstatic byte asc_to_bcd(byte asc) {

bytebcd;

if((asc >= '0') && (asc <= '9'))

bcd= (byte) (asc - '0');

elseif ((asc >= 'A') && (asc <= 'F'))

bcd= (byte) (asc - 'A' + 10);

elseif ((asc >= 'a') && (asc <= 'f'))

bcd= (byte) (asc - 'a' + 10);

else

bcd= (byte) (asc - 48);

returnbcd;

}

/**

* BCD转字符串

publicstatic String bcd2Str(byte[] bytes) {

chartemp[] = new char[bytes.length * 2], val;

for(int i = 0; i < bytes.length; i++) {

val= (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);

temp[i* 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

val= (char) (bytes[i] & 0x0f);

temp[i* 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

}

returnnew String(temp);

}

/**

* 拆分字符串

publicstatic String[] splitString(String string, int len) {

intx = string.length() / len;

inty = string.length() % len;

intz = 0;

if(y != 0) {

z= 1;

}

String[]strings = new String[x + z];

Stringstr = "";

for(int i = 0; i < x + z; i++) {

if(i == x + z - 1 && y != 0) {

str= string.substring(i * len, i * len + y);

}else {

str= string.substring(i * len, i * len + len);

}

strings[i] = str;

}

returnstrings;

}

/**

* 拆分数组

publicstatic byte[][] splitArray(byte[] data, int len) {

intx = data.length / len;

inty = data.length % len;

intz = 0;

if(y != 0) {

z= 1;

}

byte[][]arrays = new byte[x + z][];

byte[]arr;

for(int i = 0; i < x + z; i++) {

arr= new byte[len];

if(i == x + z - 1 && y != 0) {

System.arraycopy(data,i * len, arr, 0, y);

}else {

System.arraycopy(data,i * len, arr, 0, len);

}

arrays[i]= arr;

}

returnarrays;

}

需要引入jar

3. jsp页面

<scripttype="text/javascript" src="<%=basePath%>js/jquery.min.js"></script>

var key =RSAUtils.getKeyPair(publicexp,privateexp,moudel);

axes = axes.split("").reverse().join("");

returnRSAUtils.encryptedString(key,data);

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