java非對稱加密的源代碼(rsa)

java非對稱加密的源代碼rsa有哪些基本知識，下面yjbys小編為大家一一講解!

鑑於rsa加密的重要性和相關源代碼的匱乏，經過整理特此貼出。需要下載。

import er;

import rity.*;

import ublicKeySpec;

import rivateKeySpec;

import lidKeySpecException;

import rivateKey;

import ublicKey;

import .*;

import nteger;

/**

* RSA 工具類。提供加密，解密，生成密鑰對等方法。

* 需要到下載。

*

*/

public class RSAUtil {

/**

* 生成密鑰對

* @return KeyPair

* @throws EncryptException

*/

public static KeyPair generateKeyPair() throws EncryptException {

try {

KeyPairGenerator keyPairGen = nstance("RSA",

new cyCastleProvider());

final int KEY_SIZE = 1024;//沒什麼好説的'了，這個值關係到塊加密的大小，可以更改，但是不要太大，否則效率會低

ialize(KEY_SIZE, new SecureRandom());

KeyPair keyPair = eyPair();

return keyPair;

} catch (Exception e) {

throw new EncryptException(essage());

}

}

/**

* 生成公鑰

* @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());

}

}

/**

* 生成私鑰

* @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 加密的密鑰

* @param data 待加密的明文數據

* @return 加密後的數據

* @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();//獲得加密塊大小，如:加密前數據為128個byte，而key_size=1024 加密塊大小為127 byte,加密後為128個byte;因此共有2個加密塊，第一個127 byte第二個為1個byte

int outputSize = utputSize(th);//獲得加密塊加密後塊大小

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);

//這裏面doUpdate方法不可用，查看源代碼後發現每次doUpdate後並沒有什麼實際動作除了把byte[]放到ByteArrayOutputStream中，而最後doFinal的時候才將所有的byte[]進行加密，可是到了此時加密塊大小很可能已經超出了OutputSize所以只好用dofinal方法。

i++;

}

return raw;

} catch (Exception e) {

throw new EncryptException(essage());

}

}

/**

* 解密

* @param key 解密的密鑰

* @param raw 已經加密的數據

* @return 解密後的明文

* @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();

}

}

加密可以用公鑰，解密用私鑰;或者加密用私鑰。通常非對稱加密是非常消耗資源的，因此可以對大數據用對稱加密如:des(具體代碼可以看我以前發的貼子)，而對其對稱密鑰進行非對稱加密，這樣既保證了數據的安全，還能保證效率。