對稱加密演算法是以一種使用頻率高的初等的加密演算法,如你所想,之所以稱之為對稱加密演算法,說明加密祕鑰是相同,加密過程可逆,而前面介紹的base64加密,和訊息摘要加密演算法是不可逆的.一般的對稱加密演算法有DES,DES祕鑰長度不夠,易被破解,進而衍生出了3DES,在DES的基礎上又出現了AES演算法,還有PBE,IDEA等演算法.
DES(Data Encryption Standrad)資料加密標準

程式碼實現

• jdk實現

try {
            //生成key
            KeyGenerator keyGenerator = KeyGenerator.getInstance("DES");
            keyGenerator.init(56);
            SecretKey secretKey = keyGenerator.generateKey();
 

            byte[] bytesKey = secretKey.getEncoded();
            //key轉換
            KeySpec keySpec = new DESKeySpec(bytesKey);
            SecretKeyFactory factory = SecretKeyFactory.getInstance("DES");
            SecretKey convertSecretKey = factory.generateSecret(keySpec);

            //加密
            Cipher cipher = Cipher.getInstance
 
("DES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, convertSecretKey);
            byte[] result = cipher.doFinal(str.getBytes());
            System.out.println("jdk des en:"+ Hex.toHexString(result));

            //解密
            cipher.init(Cipher.DECRYPT_MODE, convertSecretKey);
            byte[] raw = cipher.doFinal(result);
            System.out.println("jdk des de:"+ new String(raw)); 
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

• bc的實現

try {
            Security.addProvider(new BouncyCastleProvider());
            //生成key
            KeyGenerator keyGenerator = KeyGenerator.getInstance("DES","BC");
            keyGenerator.init(56);
            System.out.println(keyGenerator.getProvider());
            SecretKey secretKey = keyGenerator.generateKey();
            byte[] bytesKey = secretKey.getEncoded();
            //key轉換
            KeySpec keySpec = new DESKeySpec(bytesKey);
            SecretKeyFactory factory = SecretKeyFactory.getInstance("DES");
            SecretKey convertSecretKey = factory.generateSecret(keySpec);

            //加密
            Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, convertSecretKey);
            byte[] result = cipher.doFinal(str.getBytes());
            System.out.println("jdk des en:"+ Hex.toHexString(result));

            //解密
            cipher.init(Cipher.DECRYPT_MODE, convertSecretKey);
            byte[] raw = cipher.doFinal(result);
            System.out.println("bc des de:"+ new String(raw));

        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

3DES在實際應用中十分廣泛,但效率比較低,下面是jdk實現3DES

try {
            //生成key
            KeyGenerator keyGenerator = KeyGenerator.getInstance("DESede");
//          keyGenerator.init(168);
            keyGenerator.init(new SecureRandom());//生成預設長度
            SecretKey secretKey = keyGenerator.generateKey();
            byte[] bytesKey = secretKey.getEncoded();
            //key轉換
            KeySpec keySpec = new DESedeKeySpec(bytesKey);
            SecretKeyFactory factory = SecretKeyFactory.getInstance("DESede");
            SecretKey convertSecretKey = factory.generateSecret(keySpec);

            //加密
            Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, convertSecretKey);
            byte[] result = cipher.doFinal(str.getBytes());
            System.out.println("jdk 3des en:"+ Hex.toHexString(result));

            //解密
            cipher.init(Cipher.DECRYPT_MODE, convertSecretKey);
            byte[] raw = cipher.doFinal(result);
            System.out.println("jdk 3des de:"+ new String(raw));
            } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

AES是DES演算法的代替者,目前還沒有被破解的訊息.

java實現AES與實現DES相似

        try {
            //生成key
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(new SecureRandom());
            SecretKey secretKye = keyGenerator.generateKey();
            byte[] keyBytes =  secretKye.getEncoded();
            //轉換key
            SecretKeySpec keySpec= new SecretKeySpec(keyBytes, "AES");

            //加密
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, keySpec);
            byte[] result = cipher.doFinal(str.getBytes());
            System.out.println("jdk aes en:"+ Base64.encodeBase64String(result));
            //解密
            cipher.init(Cipher.DECRYPT_MODE,  keySpec);
            byte[] raw = cipher.doFinal(result);
            System.out.println("jdk aes de:"+new String(raw));
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

PBE(Password Based Encryption)基於口令的加密
演算法結合了訊息摘要演算法和對稱加密演算法的特點,是對已有演算法是包裝(口令+鹽)

程式碼實現

try {
            //初始化鹽
            SecureRandom secureRandom = new SecureRandom();
            byte[] salt = secureRandom.generateSeed(8);
            salt = new byte[]{'a','a','a','a','a','a','a','a'};
            //口令與祕鑰
            String password = "yexiu";
            PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray());
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBEWITHMD5andDES");
            Key key = factory.generateSecret(pbeKeySpec);

            //加密
            PBEParameterSpec parameter = new PBEParameterSpec(salt, 100);
            Cipher cipher = Cipher.getInstance("PBEWITHMD5andDES");
            cipher.init(Cipher.ENCRYPT_MODE, key, parameter);
            byte[] result = cipher.doFinal(str.getBytes());
            System.out.println("jdk pbe en:"+Base64.encodeBase64String(result));

            //解密
            cipher.init(Cipher.DECRYPT_MODE, key, parameter);
            byte[] raw = cipher.doFinal(result);
            System.out.println("jdk pbe de:"+new String(raw));
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }