rsacrypto.java

1、对称密码技术的实现（单重DES加密/解密）； 2、非对称密码技术的实现（RSA

package test;
import java.security.KeyPair; 
import java.security.KeyPairGenerator; 
import java.security.PrivateKey; 
import java.security.PublicKey; 
import java.security.SecureRandom; 

import javax.crypto.Cipher; 

public class RSACrypto 
{ 
private final static String RSA = "RSA"; 
public static PublicKey uk; 
public static PrivateKey rk; 

public static void generateKey() throws Exception 
{ 
KeyPairGenerator gen = KeyPairGenerator.getInstance(RSA); 
gen.initialize(512, new SecureRandom()); 
KeyPair keyPair = gen.generateKeyPair(); 
uk = keyPair.getPublic(); 
rk = keyPair.getPrivate(); 
} 

private static byte[] encrypt(String text, PublicKey pubRSA) throws Exception 
{ 
Cipher cipher = Cipher.getInstance(RSA); 
cipher.init(Cipher.ENCRYPT_MODE, pubRSA); 
return cipher.doFinal(text.getBytes()); 
} 

public final static String encrypt(String text) 
{ 
try { 
return byte2hex(encrypt(text, uk)); 
} 
catch(Exception e) 
{ 
e.printStackTrace(); 
} 
return null; 
} 

public final static String decrypt(String data) 
{ 
try{ 
return new String(decrypt(hex2byte(data.getBytes()))); 
} 
catch (Exception e) 
{ 
e.printStackTrace(); 
} 
return null; 
} 

private static byte[] decrypt(byte[] src) throws Exception 
{ 
Cipher cipher = Cipher.getInstance(RSA); 
cipher.init(Cipher.DECRYPT_MODE, rk); 
return cipher.doFinal(src); 
} 

public static String byte2hex(byte[] b) 
{ 
String hs = ""; 
String stmp = ""; 
for (int n = 0; n < b.length; n ++) 
{ 
stmp = Integer.toHexString(b[n] & 0xFF); 
if (stmp.length() == 1) 
hs += ("0" + stmp); 
else 
hs += stmp; 
} 
return hs.toUpperCase(); 
} 

public static byte[] hex2byte(byte[] b) 
{ 
if ((b.length % 2) != 0) 
throw new IllegalArgumentException("闀垮害涓嶆槸鍋舵暟"); 

byte[] b2 = new byte[b.length / 2]; 

for (int n = 0; n < b.length; n += 2) 
{ 
String item = new String(b, n, 2); 
b2[n/2] = (byte)Integer.parseInt(item, 16); 
} 
return b2; 
} 

//just for test 
public static void main(String args[]) 
{ 
try 
{ 
RSACrypto.generateKey(); 
String cipherText = RSACrypto.encrypt("asdfghjh"); 
System.out.println(cipherText); 
String plainText = RSACrypto.decrypt(cipherText); 
System.out.println(plainText); 
} 
catch(Exception e) 
{ 
e.printStackTrace(); 
} 
} 

}