Java加密技术(二)——对称加密算法DES&AES
接下来我们介绍对称加密算法,最常用的莫过于DES数据加密算法。
DES
DES-Data Encryption Standard,即数据加密算法。是IBM公司于1975年研究成功并公开发表的。DES算法的入口参数有三个:Key、Data、Mode。其中Key为8个字节共64位,是DES算法的工作密钥;Data也为8个字节64位,是要被加密或被解密的数据;Mode为DES的工作方式,有两种:加密或解密。
DES算法把64位的明文输入块变为64位的密文输出块,它所使用的密钥也是64位。
通过java代码实现如下:Coder类见 Java加密技术(一)
import java.security.Key; import java.security.SecureRandom; import javax.crypto.Cipher; import javax.crypto.KeyGenerator; import javax.crypto.SecretKey; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.DESKeySpec; /** * DES安全编码组件 * * <pre> * 支持 DES、DESede(TripleDES,就是3DES)、AES、Blowfish、RC2、RC4(ARCFOUR) * DES key size must be equal to 56 * DESede(TripleDES) key size must be equal to 112 or 168 * AES key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available * Blowfish key size must be multiple of 8, and can only range from 32 to 448 (inclusive) * RC2 key size must be between 40 and 1024 bits * RC4(ARCFOUR) key size must be between 40 and 1024 bits * 具体内容 需要关注 JDK Document http://.../docs/technotes/guides/security/SunProviders.html * </pre> * * @author 梁栋 * @version 1.0 * @since 1.0 */ public abstract class DESCoder extends Coder { /** * ALGORITHM 算法 <br> * 可替换为以下任意一种算法,同时key值的size相应改变。 * * <pre> * DES key size must be equal to 56 * DESede(TripleDES) key size must be equal to 112 or 168 * AES key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available * Blowfish key size must be multiple of 8, and can only range from 32 to 448 (inclusive) * RC2 key size must be between 40 and 1024 bits * RC4(ARCFOUR) key size must be between 40 and 1024 bits * </pre> * * 在Key toKey(byte[] key)方法中使用下述代码 * <code>SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);</code> 替换 * <code> * DESKeySpec dks = new DESKeySpec(key); * SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); * SecretKey secretKey = keyFactory.generateSecret(dks); * </code> */ public static final String ALGORITHM = "DES"; /** * 转换密钥<br> * * @param key * @return * @throws Exception */ private static Key toKey(byte[] key) throws Exception { DESKeySpec dks = new DESKeySpec(key); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); SecretKey secretKey = keyFactory.generateSecret(dks); // 当使用其他对称加密算法时,如AES、Blowfish等算法时,用下述代码替换上述三行代码 // SecretKey secretKey = new SecretKeySpec(key, ALGORITHM); return secretKey; } /** * 解密 * * @param data * @param key * @return * @throws Exception */ public static byte[] decrypt(byte[] data, String key) throws Exception { Key k = toKey(decryptBASE64(key)); Cipher cipher = Cipher.getInstance(ALGORITHM); cipher.init(Cipher.DECRYPT_MODE, k); return cipher.doFinal(data); } /** * 加密 * * @param data * @param key * @return * @throws Exception */ public static byte[] encrypt(byte[] data, String key) throws Exception { Key k = toKey(decryptBASE64(key)); Cipher cipher = Cipher.getInstance(ALGORITHM); cipher.init(Cipher.ENCRYPT_MODE, k); return cipher.doFinal(data); } /** * 生成密钥 * * @return * @throws Exception */ public static String initKey() throws Exception { return initKey(null); } /** * 生成密钥 * * @param seed * @return * @throws Exception */ public static String initKey(String seed) throws Exception { SecureRandom secureRandom = null; if (seed != null) { secureRandom = new SecureRandom(decryptBASE64(seed)); } else { secureRandom = new SecureRandom(); } KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM); kg.init(secureRandom); SecretKey secretKey = kg.generateKey(); return encryptBASE64(secretKey.getEncoded()); } }
延续上一个类的实现,我们通过MD5以及SHA对字符串加密生成密钥,这是比较常见的密钥生成方式。
再给出一个测试类:
import static org.junit.Assert.*; import org.junit.Test; /** * * @author 梁栋 * @version 1.0 * @since 1.0 */ public class DESCoderTest { @Test public void test() throws Exception { String inputStr = "DES"; String key = DESCoder.initKey(); System.err.println("原文:\t" + inputStr); System.err.println("密钥:\t" + key); byte[] inputData = inputStr.getBytes(); inputData = DESCoder.encrypt(inputData, key); System.err.println("加密后:\t" + DESCoder.encryptBASE64(inputData)); byte[] outputData = DESCoder.decrypt(inputData, key); String outputStr = new String(outputData); System.err.println("解密后:\t" + outputStr); assertEquals(inputStr, outputStr); } }
得到的输出内容如下:
/** * DES key size must be equal to 56 * DESede(TripleDES) key size must be equal to 112 or 168 * AES key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available * Blowfish key size must be multiple of 8, and can only range from 32 to 448 (inclusive) * RC2 key size must be between 40 and 1024 bits * RC4(ARCFOUR) key size must be between 40 and 1024 bits **/
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