java非对称加密的源代码rsa有哪些基本知识，下面yjbys小编为大家一一讲解!
鉴于rsa加密的重要性和相关源代码的匮乏，经过整理特此贴出。需要下载。
import er;
import rity.*;
import ublicKeySpec;
import rivateKeySpec;
import lidKeySpecException;
import rivateKey;
import ublicKey;
import .*;
import nteger;
/**
* RSA 工具类。提供加密，解密，生成密钥对等方法。
* 需要到下载。
*
*/
public class RSAUtil {
/**
* 生成密钥对
* @return KeyPair
* @throws EncryptException
*/
public static KeyPair generateKeyPair() throws EncryptException {
try {
KeyPairGenerator keyPairGen = nstance("RSA",
new cyCastleProvider());
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
ialize(KEY_SIZE, new SecureRandom());
KeyPair keyPair = eyPair();
return keyPair;
} catch (Exception e) {
throw new EncryptException(essage());
}
}
/**
* 生成公钥
* @param modulus
* @param publicExponent
* @return RSAPublicKey
* @throws EncryptException
*/
public static RSAPublicKey generateRSAPublicKey(byte[] modulus, byte[] publicExponent) throws EncryptException {
KeyFactory keyFac = null;
try {
keyFac = nstance("RSA", new cyCastleProvider());
} catch (NoSuchAlgorithmException ex) {
throw new EncryptException(essage());
}
RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus), new BigInteger(publicExponent));
try {
return (RSAPublicKey) ratePublic(pubKeySpec);
} catch (InvalidKeySpecException ex) {
throw new EncryptException(essage());
}
}
/**
* 生成私钥
* @param modulus
* @param privateExponent
* @return RSAPrivateKey
* @throws EncryptException
*/
public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus, byte[] privateExponent) throws EncryptException {
KeyFactory keyFac = null;
try {
keyFac = nstance("RSA", new cyCastleProvider());
} catch (NoSuchAlgorithmException ex) {
throw new EncryptException(essage());
}
RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(modulus), new BigInteger(privateExponent));
try {
return (RSAPrivateKey) ratePrivate(priKeySpec);
} catch (InvalidKeySpecException ex) {
throw new EncryptException(essage());
}
}
/**
* 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 EncryptException {
try {
Cipher cipher = nstance("RSA", new cyCastleProvider());
(YPT_MODE, key);
int blockSize = lockSize();//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 = utputSize(th);//获得加密块加密后块大小
int leavedSize = th % blockSize;
int blocksSize = leavedSize != 0 ? th / blockSize + 1 : th / blockSize;
byte[] raw = new byte[outputSize * blocksSize];
int i = 0;
while (th - i * blockSize > 0) {
if (th - i * blockSize > blockSize)
nal(data, i * blockSize, blockSize, raw, i * outputSize);
else
nal(data, i * blockSize, th - 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) {
throw new EncryptException(essage());
}
}
/**
* 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 EncryptException {
try {
Cipher cipher = nstance("RSA", new cyCastleProvider());
(YPT_MODE, key);
int blockSize = lockSize();
ByteArrayOutputStream bout = new ByteArrayOutputStream(64);
int j = 0;
while (th - j * blockSize > 0) {
e(nal(raw, j * blockSize, blockSize));
j++;
}
return teArray();
} catch (Exception e) {
throw new EncryptException(essage());
}
}
/**
*
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
File file = new File("");
FileInputStream in = new FileInputStream(file);
ByteArrayOutputStream bout = new ByteArrayOutputStream();
byte[] tmpbuf = new byte[1024];
int count = 0;
while ((count = (tmpbuf)) != -1) {
e(tmpbuf, 0, count);
tmpbuf = new byte[1024];
}
e();
byte[] orgData = teArray();
KeyPair keyPair = rateKeyPair();
RSAPublicKey pubKey = (RSAPublicKey) ublic();
RSAPrivateKey priKey = (RSAPrivateKey) rivate();
byte[] pubModBytes = odulus()teArray();
byte[] pubPubExpBytes = ublicExponent()teArray();
byte[] priModBytes = odulus()teArray();
byte[] priPriExpBytes = rivateExponent()teArray();
RSAPublicKey recoveryPubKey = rateRSAPublicKey(pubModBytes,pubPubExpBytes);
RSAPrivateKey recoveryPriKey = rateRSAPrivateKey(priModBytes,priPriExpBytes);
byte[] raw = ypt(priKey, orgData);
file = new File("encrypt_");
OutputStream out = new FileOutputStream(file);
e(raw);
e();
byte[] data = ypt(recoveryPubKey, raw);
file = new File("decrypt_");
out = new FileOutputStream(file);
e(data);
h();
e();
}
}
加密可以用公钥，解密用私钥;或者加密用私钥。通常非对称加密是非常消耗资源的，因此可以对大数据用对称加密如:des(具体代码可以看我以前发的贴子)，而对其对称密钥进行非对称加密，这样既保证了数据的安全，还能保证效率。
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