Java implements Base64 algorithm of encryption algorithm

One: Basic Concepts

Plaintext: information to be encrypted

Ciphertext: The encrypted plaintext

 Encryption: The process of converting plaintext to ciphertext

Encryption algorithm: conversion algorithm for converting plaintext to ciphertext

Encryption key: the key used for encryption operations through encryption algorithms

Decryption: The process of converting ciphertext to plaintext

Decryption Algorithm: Algorithm for converting ciphertext to plaintext

Decryption key: the key used for decryption operations through the decryption algorithm

Cryptanalysis: The process of inferring the original plaintext or key by analyzing the intercepted ciphertext in the view of the interceptor

Active attack: the attacker illegally invades the password system, and uses forgery, modification, deletion, etc. to inject fake news into the system to deceive

Passive attack: intercept the ciphertext and analyze and attack it against a secure system (no damage to the ciphertext)

Cryptosystem: It consists of five parts: plaintext space, ciphertext space, key space, encryption algorithm and decryption algorithm

Two: password classification

    1): Sort by time

    Classical cipher: using characters as the basic encryption unit

    Modern ciphers: the basic unit of encryption is the block of information

    2): According to the cryptographic system

name	alias	Detailed description
Symmetric cipher	Single key cipher or private key cipher	means the encryption key is the same as the decryption key
asymmetric cipher	Dual-key cryptography or public-key cryptography	It means that the encryption key is different from the decryption key, and the key is divided into a public key and a private key
Symmetric Cryptographic Algorithms	Single-key cryptography or private-key cryptography	Refers to encryption and decryption algorithms applied to symmetric ciphers
Asymmetric cryptographic algorithm	Two-drug cryptography or public key cryptography	Refers to encryption and decryption algorithms applied to asymmetric ciphers

    3): divided according to the method of plaintext processing

    Block cipher: When encrypting the value, the plaintext is divided into fixed-length groups, and each block is encrypted with the same key and algorithm, and the output is also a fixed-length ciphertext, which is mostly used for network encryption.

    Stream cipher: also known as sequence cipher, which refers to each encrypted bit or one byte of plaintext during encryption

Three: Hash function

    1): The hash function is used to verify the integrity of the data

    2): Features: unlimited length, easy calculation of hash value, irreversible hash operation process

    3): Related algorithm:

            Message Digest Algorithm MD5, SHA--Secure Hash Algorithm

Four: digital signature

    Mainly for processing messages stored in digital form

Five: Implement the Base64 algorithm

    1): Definition

           Encoding algorithm based on 64 characters

    2): Algorithm implementation

        -jdk

        -Comoons Codec

        -Bouncy Castle

    3) Code implementation

import org.apache.commons.codec.binary.Base64;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

import java.io.IOException;

/**
 * Base64 encryption algorithm
 */
public class Base64Util {
    private static String src="Use Base64 encryption algorithm";

    // use jdk
    public static void jdkBase64() throws IOException{
        //encryption
        System.out.println("====使用jdk=====");
        BASE64Encoder encoder=new BASE64Encoder();
        String encodeSrc=encoder.encode(src.getBytes());
        System.out.println("The encrypted ciphertext is: "+encodeSrc);
        // decrypt
        BASE64Decoder decoder=new BASE64Decoder();
        String decoderSrc=new String(decoder.decodeBuffer(encodeSrc));
        System.out.println("The decrypted plaintext is: "+decoderSrc);
    }

    // use Comoons Codec
    public static void ComoonsCodecBase64(){
        System.out.println("===使用Commons codec===");
        //encryption
       byte[] encodeSrc= Base64.encodeBase64(src.getBytes());
       System.out.println("Encrypted ciphertext: "+new String(encodeSrc));
       // decrypt
       byte[] decodeSrc= Base64.decodeBase64(encodeSrc);
       System.out.println("Decrypted plaintext: "+new String(decodeSrc));
    }

    // use Bouncy castle
    public static void BouncyCastleBase64(){
        System.out.println("===使用Bouncy Castle===");
        //encryption
       byte[] encodeSrc= org.bouncycastle.util.encoders.Base64.encode(src.getBytes());
       System.out.println("Encrypted ciphertext: "+new String(encodeSrc));
       // decrypt
       byte[] decodeSrc=  org.bouncycastle.util.encoders.Base64.decode(new String(encodeSrc));
       System.out.println("Decrypted ciphertext: "+new String(decodeSrc));
    }
    public static void main(String[] args){
        try {
            jdkBase64();
            ComoonsCodecBase64();
            BouncyCastleBase64();
        }catch (IOException e){
            e.printStackTrace ();
        }
    }
}

Six: Application scenarios of Base64 algorithm

    e-mail, key, certificate files