암호화 기본 코드 :: 전산쟁이의 카피질

출처 : http://www.androidsnippets.org/snippets/39/


package net.sf.andhsli.hotspotlogin;


import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;


 /** * Usage: *
 * String crypto = SimpleCrypto.encrypt(masterpassword, cleartext)
 * ...
 * String cleartext = SimpleCrypto.decrypt(masterpassword, crypto)
 * 
* @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));
 }
 }