Java使用Cipher类实现加密的过程详解

/**
 * content: 加密内容
 * slatKey: 加密的盐，16位字符串
 * vectorKey: 加密的向量，16位字符串
 */
public String encrypt(String content, String slatKey, String vectorKey) throws Exception {
 Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
 SecretKey secretKey = new SecretKeySpec(slatKey.getBytes(), "AES");
 IvParameterSpec iv = new IvParameterSpec(vectorKey.getBytes());
 cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);
 byte[] encrypted = cipher.doFinal(content.getBytes());
 return Base64.encodeBase64String(encrypted);
}

/**
 * content: 解密内容(base64编码格式)
 * slatKey: 加密时使用的盐，16位字符串
 * vectorKey: 加密时使用的向量，16位字符串
 */
public String decrypt(String base64Content, String slatKey, String vectorKey) throws Exception {
 Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
 SecretKey secretKey = new SecretKeySpec(slatKey.getBytes(), "AES");
 IvParameterSpec iv = new IvParameterSpec(vectorKey.getBytes());
 cipher.init(Cipher.DECRYPT_MODE, secretKey, iv);
 byte[] content = Base64.decodeBase64(base64Content);
 byte[] encrypted = cipher.doFinal(content);
 return new String(encrypted);
}

SecretKey secretKey = new SecretKeySpec(slatKey.getBytes(), "AES");

/**
 * 获取加密的密匙，传入的slatKey可以是任意长度的，作为SecureRandom的随机种子，
 * 而在KeyGenerator初始化时设置密匙的长度128bit(16位byte)
 */
 private static Key getSlatKey(String slatKey) throws Exception {
 KeyGenerator kgen = KeyGenerator.getInstance("AES");
 SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
 random.setSeed(slatKey.getBytes());
 kgen.init(128, random);
 Key key = kgen.generateKey();
 return key;
 }

/**
 * 根据slatKey获取公匙，传入的slatKey作为SecureRandom的随机种子
 * 若使用new SecureRandom()创建公匙，则需要记录下私匙，解密时使用
 */
 private static byte[] getPublicKey(String slatKey) throws Exception {
 KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
 SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
 random.setSeed(slatKey.getBytes());
 keyPairGenerator.initialize(1024, random);//or 2048
 KeyPair keyPair = keyPairGenerator.generateKeyPair();
 return keyPair.getPublic().getEncoded();
 }
 
 /**
 * 根据slatKey获取私匙，传入的slatKey作为SecureRandom的随机种子
 */
 private static byte[] getPrivateKey(String slatKey) throws Exception {
 KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
 SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
 random.setSeed(slatKey.getBytes());
 keyPairGenerator.initialize(1024, random);// or 2048
 KeyPair keyPair = keyPairGenerator.generateKeyPair();
 return keyPair.getPrivate().getEncoded();
 }

/**
 * 16进制工具类
 */
public class HexUtil {
 private static final char[] HEX_CHARS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

 /**
 * 十六进制转化为二进制
 */
 public static byte[] hexStrToByteArray(String hexString) {
 if (hexString == null) {
 return null;
 }
 if (hexString.length() == 0) {
 return new byte[0];
 }
 byte[] byteArray = new byte[hexString.length() / 2];
 for (int i = 0; i < byteArray.length; i++) {
 String subStr = hexString.substring(2 * i, 2 * i + 2);
 byteArray[i] = ((byte) Integer.parseInt(subStr, 16));
 }
 return byteArray;
 }

 /**
 * 二进制转化为十六进制
 */
 public static String byteArrayToHexStr(byte[] byteArray) {
 if (byteArray == null) {
 return null;
 }
 char[] hexChars = new char[byteArray.length * 2];
 for (int j = 0; j < byteArray.length; j++) {
 int v = byteArray[j] & 0xFF;
 hexChars[j * 2] = HEX_CHARS[v >>> 4];
 hexChars[j * 2 + 1] = HEX_CHARS[v & 0x0F];
 }
 return new String(hexChars);
 }
}