[转]Android 加密解密字符串

addison_lin

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));   
}   
}