rsa文件加密 java_RSA对文件进行加密和解密

package author.estone.rsa;

import javax.crypto.Cipher;

import java.security.*;

import java.security.spec.RSAPublicKeySpec;

import java.security.spec.RSAPrivateKeySpec;

import java.security.spec.InvalidKeySpecException;

import java.security.interfaces.RSAPrivateKey;

import java.security.interfaces.RSAPublicKey;

import java.io.*;

import java.math.BigInteger;

/**

* RSA 工具类。提供加密，解密，生成密钥对等方法。

*

*/

public class RSAUtil {

/**

* 生成密钥对

*

* @return KeyPair

* @throws

*/

public static KeyPair generateKeyPair() {

try {

KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",

new org.bouncycastle.jce.provider.BouncyCastleProvider());

final int KEY_SIZE = 1024;// 没什么好说的了，这个值关系到块加密的大小，可以更改，但是不要太大，否则效率会低

keyPairGen.initialize(KEY_SIZE, new SecureRandom());

KeyPair keyPair = keyPairGen.genKeyPair();

return keyPair;

} catch (Exception e) {

return null;

}

}

/**

* 生成公钥

*

* @param modulus

* @param publicExponent

* @return RSAPublicKey

* @throws

*/

public static RSAPublicKey generateRSAPublicKey(byte[] modulus,

byte[] publicExponent) {

KeyFactory keyFac = null;

try {

keyFac = KeyFactory.getInstance("RSA",

new org.bouncycastle.jce.provider.BouncyCastleProvider());

} catch (NoSuchAlgorithmException ex) {

}

RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(

modulus), new BigInteger(publicExponent));

try {

return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);

} catch (InvalidKeySpecException ex) {

return null;

}

}

/**

* 生成私钥

*

* @param modulus

* @param privateExponent

* @return RSAPrivateKey

* @throws

*/

public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus,

byte[] privateExponent) {

KeyFactory keyFac = null;

try {

keyFac = KeyFactory.getInstance("RSA",

new org.bouncycastle.jce.provider.BouncyCastleProvider());

} catch (NoSuchAlgorithmException ex) {

}

RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(

modulus), new BigInteger(privateExponent));

try {

return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);

} catch (InvalidKeySpecException ex) {

return null;

}

}

/**

* 加密

*

* @param key

* 加密的密钥

* @param data

* 待加密的明文数据

* @return 加密后的数据

* @throws

*/

public static byte[] encrypt(Key key, byte[] data) {

try {

Cipher cipher = Cipher.getInstance("RSA",

new org.bouncycastle.jce.provider.BouncyCastleProvider());

cipher.init(Cipher.ENCRYPT_MODE, key);

int blockSize = cipher.getBlockSize();// 获得加密块大小，如：加密前数据为128个byte，而key_size=1024

// 加密块大小为127

// byte,加密后为128个byte;因此共有2个加密块，第一个127

// byte第二个为1个byte

int outputSize = cipher.getOutputSize(data.length);// 获得加密块加密后块大小

int leavedSize = data.length % blockSize;

int blocksSize = leavedSize != 0 ? data.length / blockSize + 1

: data.length / blockSize;

byte[] raw = new byte[outputSize * blocksSize];

int i = 0;

while (data.length - i * blockSize > 0) {

if (data.length - i * blockSize > blockSize)

cipher.doFinal(data, i * blockSize, blockSize, raw, i

* outputSize);

else

cipher.doFinal(data, i * blockSize, data.length - i

* blockSize, raw, i * outputSize);

// 这里面doUpdate方法不可用，查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到ByteArrayOutputStream中，而最后doFinal的时候才将所有的byte[]进行加密，可是到了此时加密块大小很可能已经超出了OutputSize所以只好用dofinal方法。

i++;

}

return raw;

} catch (Exception e) {

return null;

}

}

/**

* 解密

*

* @param key

* 解密的密钥

* @param raw

* 已经加密的数据

* @return 解密后的明文

* @throws

*/

public static byte[] decrypt(Key key, byte[] raw) {

try {

Cipher cipher = Cipher.getInstance("RSA",

new org.bouncycastle.jce.provider.BouncyCastleProvider());

cipher.init(cipher.DECRYPT_MODE, key);

int blockSize = cipher.getBlockSize();

ByteArrayOutputStream bout = new ByteArrayOutputStream(64);

int j = 0;

while (raw.length - j * blockSize > 0) {

bout.write(cipher.doFinal(raw, j * blockSize, blockSize));

j++;

}

return bout.toByteArray();

} catch (Exception e) {

return null;

}

}

/**

*

* @param args

* @throws Exception

*/

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

// 读取要加密的文件

File file = new File("d:/test.html");

FileInputStream in = new FileInputStream(file);

ByteArrayOutputStream bout = new ByteArrayOutputStream();

byte[] tmpbuf = new byte[1024];

int count = 0;

while ((count = in.read(tmpbuf)) != -1) {

bout.write(tmpbuf, 0, count);

tmpbuf = new byte[1024];

}

in.close();

// 对数据文件进行加密处理

byte[] orgData = bout.toByteArray();

KeyPair keyPair = RSAUtil.generateKeyPair();

RSAPublicKey pubKey = (RSAPublicKey) keyPair.getPublic();

RSAPrivateKey priKey = (RSAPrivateKey) keyPair.getPrivate();

byte[] pubModBytes = pubKey.getModulus().toByteArray();

byte[] pubPubExpBytes = pubKey.getPublicExponent().toByteArray();

byte[] priModBytes = priKey.getModulus().toByteArray();

byte[] priPriExpBytes = priKey.getPrivateExponent().toByteArray();

RSAPublicKey recoveryPubKey = RSAUtil.generateRSAPublicKey(pubModBytes,

pubPubExpBytes);

RSAPrivateKey recoveryPriKey = RSAUtil.generateRSAPrivateKey(

priModBytes, priPriExpBytes);

// 对文件进行加密

byte[] raw = RSAUtil.encrypt(priKey, orgData);

file = new File("encrypt_result.dat");

OutputStream out = new FileOutputStream(file);

out.write(raw);

out.close();

// 对文件进行解密

byte[] data = RSAUtil.decrypt(recoveryPubKey, raw);

file = new File("decrypt_result.html");

out = new FileOutputStream(file);

out.write(data);

out.flush();

out.close();

}

}

code from :

http://code.google.com/p/jsc4/source/browse/trunk/JSC4/src/eticketApplet/RSAUtil.java?spec=svn35&r=35

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2011-03-31 16:39

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