JCE加密和解密(基础篇)

水深无声 2022-02-22 16:12 225阅读 0赞

# Cipher #

Cipher类为加密和解密提供密码功能。它构成了JCE框架的核心(引擎类)。

NullCiper是用来验证程序的有效性，并不提供具体的加密和解密实现。

# 方法详解 #

//实例化
    getInstance(String transformation)
    getInstance(String transformation,Provider provider)
    getInstance(String transformation,String provider)
    
    //注意：transFormation的表达形式--"算法/工作模式/填充模式"
    Cipher cipher = Cipher.getInstance("AES");
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    
    DECRYPT_MODE //解密模式
    ENCRYPT_MODE //加密模式
    WRAP_MODE //包装操作
    UNWRAP_MODE //解包装操作
    //初始化
    init(int opmode,Key key) //opmode对应上面常量
    init(int opmode,Key key,AlgorithmParameters params)
    init(int opmode,Key key,AlgorithmParameterSpec params)
    init(int opmode,Key key,AlgorithmParameters params,SecureRandom random)
    init(int opmode,Key key,AlgorithmParameterSpec params,SecureRandom random)
    init(int opmode,Certificate certificate)
    init(int opmode,Certificate certificate,SecureRandom random)
    
    //输入给定的字节数组完成更新
    update(byte[] input)
    update(byte[] input,int off,int len)
    //将更新结果输出到参数中
    update(byte[] input,int off,int len,byte[] output)
    update(byte[] input,int off,int len,byte[] output,int outputoffset)
    //使用缓冲的方式
    update(ByteBuffer input,ByteBuffer output)
    
    //结束多部分加密和解密操作
    doFinal()
    ...
    
    //包装密钥
    wrap(Key key)
    
    //解包装
    unwrap(byte[] wrappedKey,String wrappedKeyAlgorithm,int wrappedKeyType)
    
    //wrappedKeyType对应以下常量
    PRIVATE_KEY //私钥
    PUBLIC_KEY //公钥
    SECRET_KEY //秘密密钥
    
    //返回缓冲区中的初始化向量
    getIV()
    
    //返回指定转换的最大密钥长度
    getMaxAllowedKeyLength(String transformation)
    
    //分组加密中，每一组都有固定的长度，称为块
    getBlockSize()
    
    //获取缓冲区字节长度
    getOutputSize(int intputLen)
    
    //返回最大参数相关信息
    getMaxAllowedParameterSpec(String transformation)
    
    //获取参数
    getParameters()
    
    //获取豁免机制对象
    getExemptionMechanism()
    
    //获取算法
    getAlgorithm()
    
    //获取提供者
    getProvider()

# 实现实例 #

//包装密钥
    KeyGenerator kg = KeyGenerator.getInstance("DES");
    SecretKey secretKey = kg.generateKey();
    Cipher cipher = Cipher.getInstance(kg.getAlgorithm());
    cipher.init(Cipher.WRAP_MODE,secretKey);
    byte[] bytes = cipher.wrap(secretKey);
    
    //解包装
    Cipher cipher = Cipher.getInstance(kg.getAlgorithm());
    cipher.init(Cipher.UNWRAP_MODE,secretKey);
    byte[] bytes = cipher.unwrap(bytes,"DES",Cipher.SECRET_KEY);
    
    //加密 此处略去了实例化
    cipher.init(Cipher.ENCRYPT_MODE,secretKey);
    byte[] input = cipher.doFinal("DES DATA".getBytes());
    
    //解密 此处略去了实例化
    cipher.init(Cipher.DECRYPT_MODE,secretKey);
    byte[] output = cipher.doFinal(input);

# CipherInputStream和CipherOutputStream #

CipherInputStream(解密)和CipherOutputStream(加密)同属Cipher类的拓展，统称为密钥流。

//解密
    byte[] bytes = new BigInteger("-4299735180166341784").toByteArray(); //这个为加密时生成的密钥
    DESKeySpec desKeySpec = new DESKeySpec(bytes);
    SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
    SecretKey secretKey = skf.generateSecret(desKeySpec);
    
    Cipher cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.DECRYPT_MODE,secretKey);
    DataInputStream dataInputStream = new DataInputStream(new CipherInputStream(new FileInputStream("secret"),cipher));
    System.out.println(dataInputStream.readUTF());
    dataInputStream.close();
    
    //加密
    KeyGenerator kg = KeyGenerator.getInstance("DES");
    SecretKey secretKey = kg.generateKey();
    byte[] bytes = secretKey.getEncoded();
    System.out.println(new BigInteger(bytes)); //打印出秘密密钥的二进制
    Cipher cipher = Cipher.getInstance(kg.getAlgorithm());
    cipher.init(Cipher.ENCRYPT_MODE,secretKey);
    CipherOutputStream cis = new CipherOutputStream(new FileOutputStream(new File("secret")),cipher);
    DataOutputStream dataOutputStream = new DataOutputStream(cis);
    dataOutputStream.writeUTF("1234567890"); //要加密的原文
    dataOutputStream.flush();
    dataOutputStream.close();
    
    //原文为: 1234567890
    //加密文件内容为: !?5谊鴿pr礷?

# SealedObject #

SealedObject能够用加密算法创建对象并保护其机密性。

//构造器
    SealedObject(Serializable object,Cipher c)
    
    //获取原始对象
    getObject(Cipher c)
    getObject(Key key)
    getObject(Key key,String provider)
    
    //返回此密封对象的算法
    getAlogrithm()

# 代码演示 #

//对象加密
    
    //代加密的对象
    String input = "SealedObject";
    KeyGenerator kg = KeyGenerator.getInstance("DES");
    SecretKey sk = kg.generateKey();
    
    Cipher cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.ENCRYPT_MODE,sk);
    SealedObject sd = new SealedObject(input,cipher);
    String 
    System.out.println(sd);
    System.out.println(sd.getObject(sk));
    
    //输出结果
    javax.crypto.SealedObject@721e0f4f
    SealedObject

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