Chapter 5. AES

			
package cn.netkiller.crypto;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.MessageDigest;
import java.security.SecureRandom;

public class TestAES {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String key = "fm6I1D2HTFVVOWUKny76TThagNq5Czrv";
		String clean = "Helloworld!!!";

		try {
			byte[] encrypted = encrypt(clean, key);
			String decrypted = decrypt(encrypted, key);
			System.out.println(decrypted);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

	public static byte[] encrypt(String plainText, String key) throws Exception {
		byte[] clean = plainText.getBytes();

		// Generating IV.
		int ivSize = 16;
		byte[] iv = new byte[ivSize];
		SecureRandom random = new SecureRandom();
		random.nextBytes(iv);
		IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

		// Hashing key.
		MessageDigest digest = MessageDigest.getInstance("SHA-256");
		digest.update(key.getBytes("UTF-8"));
		byte[] keyBytes = new byte[16];
		System.arraycopy(digest.digest(), 0, keyBytes, 0, keyBytes.length);
		SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

		// Encrypt.
		Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
		cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
		byte[] encrypted = cipher.doFinal(clean);

		// Combine IV and encrypted part.
		byte[] encryptedIVAndText = new byte[ivSize + encrypted.length];
		System.arraycopy(iv, 0, encryptedIVAndText, 0, ivSize);
		System.arraycopy(encrypted, 0, encryptedIVAndText, ivSize, encrypted.length);

		return encryptedIVAndText;
	}

	public static String decrypt(byte[] encryptedIvTextBytes, String key) throws Exception {
		int ivSize = 16;
		int keySize = 16;

		// Extract IV.
		byte[] iv = new byte[ivSize];
		System.arraycopy(encryptedIvTextBytes, 0, iv, 0, iv.length);
		IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

		// Extract encrypted part.
		int encryptedSize = encryptedIvTextBytes.length - ivSize;
		byte[] encryptedBytes = new byte[encryptedSize];
		System.arraycopy(encryptedIvTextBytes, ivSize, encryptedBytes, 0, encryptedSize);

		// Hash key.
		byte[] keyBytes = new byte[keySize];
		MessageDigest md = MessageDigest.getInstance("SHA-256");
		md.update(key.getBytes());
		System.arraycopy(md.digest(), 0, keyBytes, 0, keyBytes.length);
		SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

		// Decrypt.
		Cipher cipherDecrypt = Cipher.getInstance("AES/CBC/PKCS5Padding");
		cipherDecrypt.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
		byte[] decrypted = cipherDecrypt.doFinal(encryptedBytes);

		return new String(decrypted);
	}

}			
						
			

上面是 byte 類型使用中不是很方便，尤其是WEB中作為參數傳遞的情況，所以我們使用 BASE64編碼

			
package cn.netkiller.crypto;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64.*;

/**
 * @author netkiller
 *
 */
public class aes {

	public static String encrypt(String input, String key) {
		byte[] crypted = null;
		try {
		
			SecretKeySpec skey = new SecretKeySpec(key.getBytes(), "AES");
			
			Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
			cipher.init(Cipher.ENCRYPT_MODE, skey);
			crypted = cipher.doFinal(input.getBytes());
		} catch (Exception e) {
			System.out.println(e.toString());
		}
		java.util.Base64.Encoder encoder = java.util.Base64.getEncoder();
		
		return new String(encoder.encodeToString(crypted));
	}

	public static String decrypt(String input, String key) {
		byte[] output = null;
		try {
			java.util.Base64.Decoder decoder = java.util.Base64.getDecoder();
			SecretKeySpec skey = new SecretKeySpec(key.getBytes(), "AES");
			Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
			cipher.init(Cipher.DECRYPT_MODE, skey);
			output = cipher.doFinal(decoder.decode(input));
		} catch (Exception e) {
			System.out.println(e.toString());
		}
		return new String(output);
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		String key = "mvLBiZsiTbGwrfJB";
		String data = "ABC";

		System.out.println(aes.encrypt(data, key));
		System.out.println(aes.decrypt(aes.encrypt(data, key), key));
	}

}
			
			

			
package cn.netkiller.security;

import java.util.Base64;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AES {
	private static final String initVector = "encryptionIntVec";
	private String key;

	public AES(String key) {
		// TODO Auto-generated constructor stub
		this.key = key;
	}

	public String encrypt(String value) {
		return this.encrypt(value, this.key);
	}

	public String encrypt(String value, String key) {
		try {
			IvParameterSpec ivParameterSpec = new IvParameterSpec(initVector.getBytes("UTF-8"));
			SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES");

			Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
			cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);

			byte[] encrypted = cipher.doFinal(value.getBytes());
			return Base64.getEncoder().encodeToString(encrypted);
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		return null;
	}

	public String decrypt(String encrypted) {
		return this.decrypt(encrypted, this.key);
	}

	public String decrypt(String encrypted, String key) {
		try {
			IvParameterSpec ivParameterSpec = new IvParameterSpec(initVector.getBytes("UTF-8"));
			SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES");

			Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
			cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
			byte[] original = cipher.doFinal(Base64.getDecoder().decode(encrypted));

			return new String(original);
		} catch (Exception ex) {
			ex.printStackTrace();
		}

		return null;
	}

	public static void main(String[] args) {
		// key 長度16個位元組
		String key = "www.netkiller.cn";
		System.out.println(key.length());
		AES aes = new AES(key);
		String en = aes.encrypt("Helloworld!!!");
		String de = aes.decrypt(en);
		System.out.println(en);
		System.out.println(de);

	}
}