转载请注明出处: http://blog.csdn.net/bbld_/article/details/38777491
概述
RSA是目前最有影响力的公钥加密算法,该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,即公钥,而两个大素数组合成私钥。公钥是可发布的供任何人使用,私钥则为自己所有,供解密之用。关于RSA其它需要了解的知识,参考维基百科:http://zh.wikipedia.org/zh-cn/RSA%E5%8A%A0%E5%AF%86%E6%BC%94%E7%AE%97%E6%B3%95
在项目开发中对于一些比较敏感的信息需要对其进行加密处理,我们就可以使用RSA这种非对称加密算法来对数据进行加密处理。
使用
秘钥对的生成
1、我们可以在代码里随机生成密钥对
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public static KeyPair generateRSAKeyPair(int keyLength)
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{
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try
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{
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KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);
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kpg.initialize(keyLength);
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return kpg.genKeyPair();
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} catch (NoSuchAlgorithmException e)
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{
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e.printStackTrace();
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return null;
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}
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}
通过这方法我们得到KeyPair后就可以调用 keyPair.getPrivate() 和 pair.getPublic()得到 私钥 和 公钥了。不过实际我们一般是使用2的方法把生成的密钥对保存起来,密钥自己保存,比如服务端,把公钥给客户端(Android)用于加密需要发送的数据,最后服务端根据私钥吧客户端加密的信息解密再处理。
2、通过OpenSSl工具生成密钥对
OpenSSl工具下载:OpenSSl工具 (64位的也可使用)使用OpenSSl工具生成密钥对的过程如下:
首先双击打开bin文件夹下的openssl.exe,打开之后是一个命令行窗口:

然后通过如下命令生成私钥:
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genrsa -out rsa_private_key.pem 1024

这条命令是让openssl随机生成了一份私钥,加密长度是1024位, 密钥长度,范围:512~2048。执行完命令后就可在bin文件夹下看到rsa_private_key.pem文件了。
用文本类工具打开可看到里面的内容:
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-----BEGIN RSA PRIVATE KEY-----
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MIICXQIBAAKBgQCfRTdcPIH10gT9f31rQuIInLwe7fl2dtEJ93gTmjE9c2H+kLVE
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NWgECiJVQ5sonQNfwToMKdO0b3Olf4pgBKeLThraz/L3nYJYlbqjHC3jTjUnZc0l
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uumpXGsox62+PuSGBlfb8zJO6hix4GV/vhyQVCpG9aYqgE7zyTRZYX9byQIDAQAB
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AoGAO9+sYRtKC9xJDfcocfMxv+UT/1ic6EDgcqu6Uzwq+Jvwod9KlXqyQJqCr6T7
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pjfodc3RAZOTx4gCZJverBvz053RH5GawCdocEgaqbXAAWJOhA+9IEU0NUud7ckF
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yDko0QXLoGP9tanrMEt5zMqt8QxDyl6Xcij3mk8rivOgBJECQQDNTO6dZX8xCozc
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Ne0gzC53Gv/KQXANBBHMr7WkKUb2i5+tXkEJ5z3abx2ppEQXDr4AgJH8Gtbm6K7t
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EHV4ov4FAkEAxppD/iiT1/SVQq20be8CsiHpsjTPiestWQWdm1Qn/Y2nAkGkpCFp
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yEdUvVDPtQhRN9EqNggNAnwg5kMvsuwN9QJAfHBhQe4/hk5Kyz+0l+irUW6AFOxN
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KtaIo3TtuK98X/yJsOAstAACMeCgLi9vRjqdWFiWJCVwlU38mZ0cVx8UsQJBALzt
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M5Er+LiPKw5rQCD0JZRfPnkQU/3XgyQUe4Gv5PsHLcCvwXeBcafcc3hEz9JfPyPi
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Dk2oCvg6LPHfKBkFBaECQQCODcKX6DBWiyVxmPaJOOcF63KpCYDPkjeovIUHro1x
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ElR2GrQCC/9Q4C4vruOhBQ+vX8NMPnO6NBy5TLGDwMyc
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-----END RSA PRIVATE KEY-----
这里面的内容是标准的ASCII字符,中间的一大串字符就是私钥数据了。
然后通过如下命令生成公钥:
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rsa -in rsa_private_key.pem -out rsa_public_key.pem -pubout

打开文件看下里面的内容:
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-----BEGIN PUBLIC KEY-----
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MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCfRTdcPIH10gT9f31rQuIInLwe
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7fl2dtEJ93gTmjE9c2H+kLVENWgECiJVQ5sonQNfwToMKdO0b3Olf4pgBKeLThra
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z/L3nYJYlbqjHC3jTjUnZc0luumpXGsox62+PuSGBlfb8zJO6hix4GV/vhyQVCpG
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9aYqgE7zyTRZYX9byQIDAQAB
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-----END PUBLIC KEY-----
可以看到是跟私钥的文件类似的。
这样密钥就基本生成了,不过这样密钥对的私钥是无法在代码中直接使用的,要想使用它需要借助RSAPrivateKeyStructure这个类,java是不自带的。所以为了方便使用,我们需要对私钥进行PKCS#8编码,命令如下:
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pkcs8 -topk8 -in rsa_private_key.pem -out pkcs8_rsa_private_key.pem -nocrypt

这条命令的结果依然是在bin文件夹生成了pkcs8_rsa_private_key.pem文件,打开内容如下:
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-----BEGIN PRIVATE KEY-----
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MIICdwIBADANBgkqhkiG9w0BAQEFAASCAmEwggJdAgEAAoGBAJ9FN1w8gfXSBP1/
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fWtC4gicvB7t+XZ20Qn3eBOaMT1zYf6QtUQ1aAQKIlVDmyidA1/BOgwp07Rvc6V/
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imAEp4tOGtrP8vedgliVuqMcLeNONSdlzSW66alcayjHrb4+5IYGV9vzMk7qGLHg
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ZX++HJBUKkb1piqATvPJNFlhf1vJAgMBAAECgYA736xhG0oL3EkN9yhx8zG/5RP/
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WJzoQOByq7pTPCr4m/Ch30qVerJAmoKvpPumN+h1zdEBk5PHiAJkm96sG/PTndEf
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kZrAJ2hwSBqptcABYk6ED70gRTQ1S53tyQXIOSjRBcugY/21qeswS3nMyq3xDEPK
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XpdyKPeaTyuK86AEkQJBAM1M7p1lfzEKjNw17SDMLnca/8pBcA0EEcyvtaQpRvaL
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n61eQQnnPdpvHamkRBcOvgCAkfwa1uboru0QdXii/gUCQQDGmkP+KJPX9JVCrbRt
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7wKyIemyNM+J6y1ZBZ2bVCf9jacCQaSkIWnIR1S9UM+1CFE30So2CA0CfCDmQy+y
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7A31AkB8cGFB7j+GTkrLP7SX6KtRboAU7E0q1oijdO24r3xf/Imw4Cy0AAIx4KAu
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L29GOp1YWJYkJXCVTfyZnRxXHxSxAkEAvO0zkSv4uI8rDmtAIPQllF8+eRBT/deD
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JBR7ga/k+wctwK/Bd4Fxp9xzeETP0l8/I+IOTagK+Dos8d8oGQUFoQJBAI4Nwpfo
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MFaLJXGY9ok45wXrcqkJgM+SN6i8hQeujXESVHYatAIL/1DgLi+u46EFD69fw0w+
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c7o0HLlMsYPAzJw=
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-----END PRIVATE KEY-----
可以看到中间的私钥内容有所变化了,这样的私钥我们在代码里就方便使用了。
以上的密钥文件使用时需要注意吧头和尾的字符串去掉,我们只取中间的内容。
代码中的使用
首先我们需要封装写个RSA的工具类,方便加密解密的操作。
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package com.example.rsa;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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import java.math.BigInteger;
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import java.security.KeyFactory;
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import java.security.KeyPair;
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import java.security.KeyPairGenerator;
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import java.security.NoSuchAlgorithmException;
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import java.security.PrivateKey;
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import java.security.PublicKey;
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import java.security.interfaces.RSAPrivateKey;
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import java.security.interfaces.RSAPublicKey;
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import java.security.spec.InvalidKeySpecException;
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import java.security.spec.PKCS8EncodedKeySpec;
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import java.security.spec.RSAPublicKeySpec;
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import java.security.spec.X509EncodedKeySpec;
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import javax.crypto.Cipher;
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public final class RSAUtils
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{
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private static String RSA = "RSA";
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public static KeyPair generateRSAKeyPair()
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{
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return generateRSAKeyPair(1024);
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}
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public static KeyPair generateRSAKeyPair(int keyLength)
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{
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try
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{
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KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);
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kpg.initialize(keyLength);
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return kpg.genKeyPair();
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} catch (NoSuchAlgorithmException e)
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{
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e.printStackTrace();
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return null;
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}
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}
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public static byte[] encryptData(byte[] data, PublicKey publicKey)
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{
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try
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{
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Cipher cipher = Cipher.getInstance(RSA);
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cipher.init(Cipher.ENCRYPT_MODE, publicKey);
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return cipher.doFinal(data);
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} catch (Exception e)
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{
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e.printStackTrace();
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return null;
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}
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}
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public static byte[] decryptData(byte[] encryptedData, PrivateKey privateKey)
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{
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try
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{
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Cipher cipher = Cipher.getInstance(RSA);
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cipher.init(Cipher.DECRYPT_MODE, privateKey);
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return cipher.doFinal(encryptedData);
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} catch (Exception e)
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{
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return null;
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}
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}
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public static PublicKey getPublicKey(byte[] keyBytes) throws NoSuchAlgorithmException,
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InvalidKeySpecException
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{
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X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
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KeyFactory keyFactory = KeyFactory.getInstance(RSA);
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PublicKey publicKey = keyFactory.generatePublic(keySpec);
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return publicKey;
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}
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public static PrivateKey getPrivateKey(byte[] keyBytes) throws NoSuchAlgorithmException,
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InvalidKeySpecException
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{
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PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
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KeyFactory keyFactory = KeyFactory.getInstance(RSA);
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PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
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return privateKey;
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}
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public static PublicKey getPublicKey(String modulus, String publicExponent)
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throws NoSuchAlgorithmException, InvalidKeySpecException
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{
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BigInteger bigIntModulus = new BigInteger(modulus);
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BigInteger bigIntPrivateExponent = new BigInteger(publicExponent);
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RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
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KeyFactory keyFactory = KeyFactory.getInstance(RSA);
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PublicKey publicKey = keyFactory.generatePublic(keySpec);
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return publicKey;
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}
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public static PrivateKey getPrivateKey(String modulus, String privateExponent)
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throws NoSuchAlgorithmException, InvalidKeySpecException
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{
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BigInteger bigIntModulus = new BigInteger(modulus);
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BigInteger bigIntPrivateExponent = new BigInteger(privateExponent);
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RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
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KeyFactory keyFactory = KeyFactory.getInstance(RSA);
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PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
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return privateKey;
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}
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public static PublicKey loadPublicKey(String publicKeyStr) throws Exception
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{
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try
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{
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byte[] buffer = Base64Utils.decode(publicKeyStr);
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KeyFactory keyFactory = KeyFactory.getInstance(RSA);
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X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
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return (RSAPublicKey) keyFactory.generatePublic(keySpec);
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} catch (NoSuchAlgorithmException e)
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{
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throw new Exception("无此算法");
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} catch (InvalidKeySpecException e)
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{
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throw new Exception("公钥非法");
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} catch (NullPointerException e)
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{
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throw new Exception("公钥数据为空");
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}
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}
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public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception
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{
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try
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{
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byte[] buffer = Base64Utils.decode(privateKeyStr);
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PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
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KeyFactory keyFactory = KeyFactory.getInstance(RSA);
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return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
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} catch (NoSuchAlgorithmException e)
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{
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throw new Exception("无此算法");
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} catch (InvalidKeySpecException e)
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{
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throw new Exception("私钥非法");
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} catch (NullPointerException e)
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{
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throw new Exception("私钥数据为空");
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}
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}
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public static PublicKey loadPublicKey(InputStream in) throws Exception
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{
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try
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{
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return loadPublicKey(readKey(in));
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} catch (IOException e)
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{
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throw new Exception("公钥数据流读取错误");
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} catch (NullPointerException e)
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{
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throw new Exception("公钥输入流为空");
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}
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}
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public static PrivateKey loadPrivateKey(InputStream in) throws Exception
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{
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try
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{
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return loadPrivateKey(readKey(in));
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} catch (IOException e)
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{
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throw new Exception("私钥数据读取错误");
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} catch (NullPointerException e)
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{
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throw new Exception("私钥输入流为空");
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}
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}
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private static String readKey(InputStream in) throws IOException
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{
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BufferedReader br = new BufferedReader(new InputStreamReader(in));
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String readLine = null;
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StringBuilder sb = new StringBuilder();
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while ((readLine = br.readLine()) != null)
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{
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if (readLine.charAt(0) == '-')
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{
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continue;
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} else
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{
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sb.append(readLine);
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sb.append('\r');
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}
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}
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return sb.toString();
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}
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public static void printPublicKeyInfo(PublicKey publicKey)
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{
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RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey;
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System.out.println("----------RSAPublicKey----------");
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System.out.println("Modulus.length=" + rsaPublicKey.getModulus().bitLength());
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System.out.println("Modulus=" + rsaPublicKey.getModulus().toString());
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System.out.println("PublicExponent.length=" + rsaPublicKey.getPublicExponent().bitLength());
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System.out.println("PublicExponent=" + rsaPublicKey.getPublicExponent().toString());
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}
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public static void printPrivateKeyInfo(PrivateKey privateKey)
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{
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RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) privateKey;
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System.out.println("----------RSAPrivateKey ----------");
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System.out.println("Modulus.length=" + rsaPrivateKey.getModulus().bitLength());
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System.out.println("Modulus=" + rsaPrivateKey.getModulus().toString());
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System.out.println("PrivateExponent.length=" + rsaPrivateKey.getPrivateExponent().bitLength());
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System.out.println("PrivatecExponent=" + rsaPrivateKey.getPrivateExponent().toString());
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}
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}
上面需要注意的就是加密是有长度限制的,过长的话会抛异常!!!
代码中有些需要使用Base64再转换的,而java中不自带,Android中自带,所以自己写出一个来,方便Java后台使用
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package com.example.rsa;
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import java.io.UnsupportedEncodingException;
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public class Base64Utils
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{
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private static char[] base64EncodeChars = new char[]
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{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
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'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
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'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
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'6', '7', '8', '9', '+', '/' };
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private static byte[] base64DecodeChars = new byte[]
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{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
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54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
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12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29,
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30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1,
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-1, -1, -1 };
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public static String encode(byte[] data)
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{
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StringBuffer sb = new StringBuffer();
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int len = data.length;
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int i = 0;
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int b1, b2, b3;
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while (i < len)
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{
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b1 = data[i++] & 0xff;
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if (i == len)
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{
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sb.append(base64EncodeChars[b1 >>> 2]);
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sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
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sb.append("==");
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break;
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}
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b2 = data[i++] & 0xff;
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if (i == len)
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{
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sb.append(base64EncodeChars[b1 >>> 2]);
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sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
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sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
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sb.append("=");
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break;
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}
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b3 = data[i++] & 0xff;
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sb.append(base64EncodeChars[b1 >>> 2]);
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sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
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sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);
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sb.append(base64EncodeChars[b3 & 0x3f]);
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}
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return sb.toString();
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}
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-
-
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public static byte[] decode(String str)
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{
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try
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{
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return decodePrivate(str);
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} catch (UnsupportedEncodingException e)
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{
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e.printStackTrace();
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}
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return new byte[]
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{};
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}
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private static byte[] decodePrivate(String str) throws UnsupportedEncodingException
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{
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StringBuffer sb = new StringBuffer();
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byte[] data = null;
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data = str.getBytes("US-ASCII");
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int len = data.length;
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int i = 0;
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int b1, b2, b3, b4;
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while (i < len)
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{
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do
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{
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b1 = base64DecodeChars[data[i++]];
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} while (i < len && b1 == -1);
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if (b1 == -1)
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break;
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do
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{
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b2 = base64DecodeChars[data[i++]];
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} while (i < len && b2 == -1);
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if (b2 == -1)
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break;
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sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4)));
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do
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{
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b3 = data[i++];
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if (b3 == 61)
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return sb.toString().getBytes("iso8859-1");
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b3 = base64DecodeChars[b3];
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} while (i < len && b3 == -1);
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if (b3 == -1)
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break;
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sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));
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do
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{
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b4 = data[i++];
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if (b4 == 61)
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return sb.toString().getBytes("iso8859-1");
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b4 = base64DecodeChars[b4];
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} while (i < len && b4 == -1);
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if (b4 == -1)
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break;
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sb.append((char) (((b3 & 0x03) << 6) | b4));
-
}
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return sb.toString().getBytes("iso8859-1");
-
}
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-
}
最后就是真正使用它们了:
我把密钥放到assest资源文件夹里了,也可以直接使用字符串得到,上面注释掉了。
最后我们来看下效果吧:

源码下载地址:http://download.csdn.net/detail/bbld_/7806673