这个问题搞了好几天了，还是没弄出来，代码如下：
[code="java"]
import javax.crypto.Cipher;
import java.security.*;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.RSAPrivateKeySpec;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.io.*;
import java.math.BigInteger;
public class RSAUtil {
/**
* 生成密钥对
* @return KeyPair
* @throws EncryptException
*/
public static KeyPair generateKeyPair() throws Exception {
try {
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
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;
}
finally{}
}
/**
* 生成公钥
* @param modulus
* @param publicExponent
* @return RSAPublicKey
* @throws EncryptException
*/
public static RSAPublicKey generateRSAPublicKey(byte[] modulus, byte[] publicExponent) throws Exception {
KeyFactory keyFac = null;
try {
keyFac = KeyFactory.getInstance("RSA");
} catch (NoSuchAlgorithmException ex) {
throw new Exception(ex.getMessage());
}
RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus), new BigInteger(publicExponent));
try {
return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);
} finally{}
}
/**
* 生成私钥
* @param modulus
* @param privateExponent
* @return RSAPrivateKey
* @throws EncryptException
*/
public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus, byte[] privateExponent) throws Exception {
KeyFactory keyFac = null;
try {
keyFac = KeyFactory.getInstance("RSA");
} catch (NoSuchAlgorithmException ex) {
throw new Exception(ex.getMessage());
}
RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(modulus), new BigInteger(privateExponent));
try {
return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);
} finally{}
}
/**
* 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 EncryptException
*/
public static byte[] encrypt(Key key, byte[] data) throws Exception {
try {
Cipher cipher = Cipher.getInstance("RSA");
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;
}
finally{}
}
/**
* 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 EncryptException
*/
public static byte[] decrypt(Key key, byte[] raw) throws Exception {
try {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, key);
int blockSize = cipher.getBlockSize();
ByteArrayOutputStream bout = new ByteArrayOutputStream(64);
int j = 0;
while (raw.length - j * blockSize > 0) {
if (raw.length - j * blockSize > blockSize)
bout.write(cipher.doFinal(raw, j * blockSize, blockSize));
else
bout.write(cipher.doFinal(raw, j * blockSize, raw.length - j * blockSize));
j++;
}
return bout.toByteArray();
} finally{}
}
/**
*
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
File file=null;
FileInputStream in = new FileInputStream("d:/MyPhoto.jpg");
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();
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();
RSAPublicKey recoveryPubKey = RSAUtil.generateRSAPublicKey(pubModBytes,pubPubExpBytes);
byte[] raw = RSAUtil.encrypt(priKey, orgData);
file = new File("d:/Photo.dat");
OutputStream out = new FileOutputStream(file);
out.write(raw);
out.close();
byte[] data = RSAUtil.decrypt(recoveryPubKey, raw);
file = new File("d:/Photo.jpg");
out = new FileOutputStream(file);
out.write(data);
out.flush();
out.close();
}
}
[/code]
在MyEclipse运行时错误提示为：
Exception in thread "main" java.lang.ArithmeticException: / by zero
at RSA.RSAUtil.encrypt(RSAUtil.java:84)
at RSA.RSAUtil.main(RSAUtil.java:152)
希望有人能给解决一下，先谢谢了
