最簡單的DES加密演算法實現

Base64.java

package com.mstf.des;
 
import java.io.UnsupportedEncodingException;
 
/**
 * base64編碼/解碼
 * @author ceet
 *
 */
public class Base64 {
 
	public static String encode(String data) {
		return new String(encode(data.getBytes()));
	}
 
	public static String decode(String data) {
		try {
			return new String(decode(data.toCharArray()),"utf-8");
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
			return null;
		}	
	}
 
	private static char[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
			.toCharArray();
 
	private static byte[] codes = new byte[256];
 
	static {
		for (int i = 0; i < 256; i++) {
			codes[i] = -1;
		}
		for (int i = 'A'; i <= 'Z'; i++) {
			codes[i] = (byte) (i - 'A');
		}
 
		for (int i = 'a'; i <= 'z'; i++) {
			codes[i] = (byte) (26 + i - 'a');
		}
		for (int i = '0'; i <= '9'; i++) {
			codes[i] = (byte) (52 + i - '0');
		}
		codes['+'] = 62;
		codes['/'] = 63;
	}
 
	public static char[] encode(byte[] data) {
		char[] out = new char[((data.length + 2) / 3) * 4];
		for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
			boolean quad = false;
			boolean trip = false;
 
			int val = (0xFF & (int) data[i]);
			val <<= 8;
			if ((i + 1) < data.length) {
				val |= (0xFF & (int) data[i + 1]);
				trip = true;
			}
			val <<= 8;
			if ((i + 2) < data.length) {
				val |= (0xFF & (int) data[i + 2]);
				quad = true;
			}
			out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
			val >>= 6;
			out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
			val >>= 6;
			out[index + 1] = alphabet[val & 0x3F];
			val >>= 6;
			out[index + 0] = alphabet[val & 0x3F];
		}
		return out;
	}
 
	public static byte[] decode(char[] data) {
		int tempLen = data.length;
		for (int ix = 0; ix < data.length; ix++) {
			if ((data[ix] > 255) || codes[data[ix]] < 0) {
				--tempLen;
			}
		}
		int len = (tempLen / 4) * 3;
		if ((tempLen % 4) == 3) {
			len += 2;
		}
		if ((tempLen % 4) == 2) {
			len += 1;
 
		}
		byte[] out = new byte[len];
 
		int shift = 0;
		int accum = 0;
		int index = 0;
 
		for (int ix = 0; ix < data.length; ix++) {
			int value = (data[ix] > 255) ? -1 : codes[data[ix]];
 
			if (value >= 0) {
				accum <<= 6;
				shift += 6;
				accum |= value;
				if (shift >= 8) {
					shift -= 8;
					out[index++] = (byte) ((accum >> shift) & 0xff);
				}
			}
		}
 
		if (index != out.length) {
			throw new Error("Miscalculated data length (wrote " + index
					+ " instead of " + out.length + ")");
		}
 
		return out;
	}
}

DESUtil.java

package com.mstf.des;
 
import java.security.Key;
import java.security.SecureRandom;
 
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
 
/**
 * DES對稱演算法(加密/解密)
 * 
 * @author ceet
 *
 */
public class DESUtil {
 
	private Key key;
 
	public DESUtil(String strKey) {
		setKey(strKey);
	}
 
	public void setKey(String strKey) {
		try {
			KeyGenerator generator = KeyGenerator.getInstance("DES");
			generator.init(new SecureRandom(strKey.getBytes())); // 根據參數生成key
			this.key = generator.generateKey();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
 
	public String encrypt(String source) {
		return encrypt(source, "utf-8");
	}
 
	public String decrypt(String encryptedData) {
		return decrypt(encryptedData, "utf-8");
	}
 
	public String encrypt(String source, String charSet) {
		String encrypt = null;
		try {
			byte[] ret = encrypt(source.getBytes(charSet));
			encrypt = new String(Base64.encode(ret));
		} catch (Exception e) {
			e.printStackTrace();
			encrypt = null;
		}
		return encrypt;
	}
 
	public String decrypt(String encryptedData, String charSet) {
		String descryptedData = null;
		try {
			byte[] ret = descrypt(Base64.decode(encryptedData.toCharArray()));
			descryptedData = new String(ret, charSet);
		} catch (Exception e) {
			e.printStackTrace();
			descryptedData = null;
		}
		return descryptedData;
	}
 
	private byte[] encrypt(byte[] primaryData) {
		try {
			Cipher cipher = Cipher.getInstance("DES"); // Cipher對象實際完成加密操作
			cipher.init(Cipher.ENCRYPT_MODE, this.key); // 用密鑰初始化Cipher對象(加密)
 
			return cipher.doFinal(primaryData);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}
 
	private byte[] descrypt(byte[] encryptedData) {
		try {
			Cipher cipher = Cipher.getInstance("DES"); // Cipher對象實際完成解密操作
			cipher.init(Cipher.DECRYPT_MODE, this.key); // 用密鑰初始化Cipher對象(解密)
 
			return cipher.doFinal(encryptedData);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}
 
	public static void main(String[] args) {
		String code = "ceet";
		DESUtil desUtil = new DESUtil("key");
		String encrypt = desUtil.encrypt(code);
		String decrypt = desUtil.decrypt(encrypt);
		System.out.println("原內容：" + code);
		System.out.println("加密：" + encrypt);
		System.out.println("解密：" + decrypt);
	}
}