java 字符串加密 解密

package eoe.demo; 

import java.security.SecureRandom; 

import javax.crypto.Cipher; 
import javax.crypto.KeyGenerator; 
import javax.crypto.SecretKey; 
import javax.crypto.spec.SecretKeySpec; 

/** 
* Usage: 
* <pre> 
* String crypto = SimpleCrypto.encrypt(masterpassword, cleartext) 
* ... 
* String cleartext = SimpleCrypto.decrypt(masterpassword, crypto) 
* </pre> 
* @author ferenc.hechler 
*/ 
public class SimpleCrypto { 

public static String encrypt(String seed, String cleartext) throws Exception { 
byte[] rawKey = getRawKey(seed.getBytes()); 
byte[] result = encrypt(rawKey, cleartext.getBytes()); 
return toHex(result); 
} 

public static String decrypt(String seed, String encrypted) throws Exception { 
byte[] rawKey = getRawKey(seed.getBytes()); 
byte[] enc = toByte(encrypted); 
byte[] result = decrypt(rawKey, enc); 
return new String(result); 
} 

private static byte[] getRawKey(byte[] seed) throws Exception { 
KeyGenerator kgen = KeyGenerator.getInstance("AES"); 
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); 
sr.setSeed(seed); 
kgen.init(128, sr); // 192 and 256 bits may not be available 
SecretKey skey = kgen.generateKey(); 
byte[] raw = skey.getEncoded(); 
return raw; 
} 


private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception { 
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); 
Cipher cipher = Cipher.getInstance("AES"); 
cipher.init(Cipher.ENCRYPT_MODE, skeySpec); 
byte[] encrypted = cipher.doFinal(clear); 
return encrypted; 
} 

private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception { 
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); 
Cipher cipher = Cipher.getInstance("AES"); 
cipher.init(Cipher.DECRYPT_MODE, skeySpec); 
byte[] decrypted = cipher.doFinal(encrypted); 
return decrypted; 
} 

public static String toHex(String txt) { 
return toHex(txt.getBytes()); 
} 
public static String fromHex(String hex) { 
return new String(toByte(hex)); 
} 

public static byte[] toByte(String hexString) { 
int len = hexString.length()/2; 
byte[] result = new byte[len]; 
for (int i = 0; i < len; i++) 
result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue(); 
return result; 
} 

public static String toHex(byte[] buf) { 
if (buf == null) 
return ""; 
StringBuffer result = new StringBuffer(2*buf.length); 
for (int i = 0; i < buf.length; i++) { 
appendHex(result, buf[i]); 
} 
return result.toString(); 
} 
private final static String HEX = "0123456789ABCDEF"; 
private static void appendHex(StringBuffer sb, byte b) { 
sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f)); 
} 

}