在Android使用RSA 算法加解密

RSA由于public
key<公钥> 和private
key<密钥>的不同<也叫非对称算法加解密>,极大的提高了文件的安全性。 对称算法是同key的
,这样很容易被人破解。

RSA算法：

import java.security.Key;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.interfaces.RSAPrivateKey;

import java.security.interfaces.RSAPublicKey;

import java.security.spec.PKCS8EncodedKeySpec;

import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

import sun.misc.BASE64Decoder;

import sun.misc.BASE64Encoder;

public class RSAHelper {

public static PublicKey getPublicKey(String key) throws Exception {

byte[] keyBytes;

keyBytes = (new BASE64Decoder()).decodeBuffer(key);

X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PublicKey publicKey = keyFactory.generatePublic(keySpec);

return publicKey;

}

public static PrivateKey getPrivateKey(String key) throws Exception {

byte[] keyBytes;

keyBytes = (new BASE64Decoder()).decodeBuffer(key);

PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

return privateKey;

}

public static String getKeyString(Key key) throws Exception {

byte[] keyBytes = key.getEncoded();

String s = (new BASE64Encoder()).encode(keyBytes);

return s;

}

public static void main(String[] args) throws Exception {

KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");

//密钥位数

keyPairGen.initialize(1024);

//密钥对

KeyPair keyPair = keyPairGen.generateKeyPair();

// 公钥

PublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

// 私钥

PrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

String publicKeyString = getKeyString(publicKey);

System.out.println("public:/n" + publicKeyString);

String privateKeyString = getKeyString(privateKey);

System.out.println("private:/n" + privateKeyString);

//加解密类

Cipher cipher = Cipher.getInstance("RSA");//Cipher.getInstance("RSA/ECB/PKCS1Padding");

//明文

byte[] plainText = "我们都很好！邮件：@sina.com".getBytes();

//加密

cipher.init(Cipher.ENCRYPT_MODE, publicKey);

byte[] enBytes = cipher.doFinal(plainText);

//通过密钥字符串得到密钥

publicKey = getPublicKey(publicKeyString);

privateKey = getPrivateKey(privateKeyString);

//解密

cipher.init(Cipher.DECRYPT_MODE, privateKey);

byte[]deBytes = cipher.doFinal(enBytes);

publicKeyString = getKeyString(publicKey);

System.out.println("public:/n" +publicKeyString);

privateKeyString = getKeyString(privateKey);

System.out.println("private:/n" + privateKeyString);

String s = new String(deBytes);

System.out.println(s);

}

}

在实际开发中！ 我们通过自己的modulus ,publicExponent
这两个是用户加密产生public
key 而 privateExponet 用于产生private
key 来开发的情况比较多。

import java.math.BigInteger;

import java.security.KeyFactory;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.spec.RSAPrivateKeySpec;

import java.security.spec.RSAPublicKeySpec;

import javax.crypto.Cipher;

public class RsaKey {

public PublicKey getPublicKey(String modulus,String publicExponent) throws Exception {

BigInteger m = new BigInteger(modulus);

BigInteger e = new BigInteger(publicExponent);

RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m,e);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PublicKey publicKey = keyFactory.generatePublic(keySpec);

return publicKey;

}

public PrivateKey getPrivateKey(String modulus,String privateExponent) throws Exception {

BigInteger m = new BigInteger(modulus);

BigInteger e = new BigInteger(privateExponent);

RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m,e);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

return privateKey;

}

public static void main(String[] args) throws Exception {

String modulus = "10103166745709600780215616551837697832816413714471062522342538060943596036859967333870827790358555455232243383580565187280643159050869924436081447583051139";

String publicExponent = "65537";

String privateExponet = "367979294475011322800474185715497882523349856362702385535371444397399388741997039894583483410120364529325888461124714276674612930833020362278754665756193";

RsaKey key = new RsaKey();

PublicKey publicKey = key.getPublicKey(modulus, publicExponent);

PrivateKey privateKey = key.getPrivateKey(modulus, privateExponet);

//加解密类

Cipher cipher = Cipher.getInstance("RSA");
//"RSA/ECB/PKCS1Padding" 就是：“算法/工作模式/填充模式”

//明文

byte[] plainText = "hello
world !".getBytes();

//加密

cipher.init(Cipher.ENCRYPT_MODE, publicKey);

byte[] enBytes = cipher.doFinal(plainText);

cipher.init(Cipher.DECRYPT_MODE, privateKey);

byte[]deBytes = cipher.doFinal(enBytes);

String s = new String(deBytes);

System.out.println(s);

}

}