【java】Java Cryptography Extension (JCE)

在Java中，我们可以使用Java Cryptography Extension (JCE) 来实现加密和解密工具和技术。以下是一些常见的加密和解密技术及其示例代码：

1.使用AES加密和解密

package org.example.Test05;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.util.Arrays;
import java.util.Base64;

public class AESEncryption {
    private static final String ALGORITHM = "AES";

    public static String encrypt(String data, String key) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes("UTF-8"), ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
        byte[] encryptedBytes = cipher.doFinal(data.getBytes());
        return Base64.getEncoder().encodeToString(encryptedBytes);
    }

    public static String decrypt(String encryptedData, String key) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes("UTF-8"), ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
        byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(encryptedData));
        return new String(decryptedBytes);
    }

    public static void main(String[] args) throws Exception {
        String originKey = "zhegeshikey";
        byte[] extendedKey = Arrays.copyOf(originKey.getBytes("UTF-8"), 16); // 扩展到16字节
        String key = new String(extendedKey, "UTF-8");
        String encrypt = encrypt("test测试", key);
        System.out.println(encrypt);
        String decrypt = decrypt(encrypt, key);
        System.out.println(decrypt);
    }
}

2. 使用RSA加密和解密

package org.example.Test05;

import javax.crypto.Cipher;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

public class RSAEncryption {
    private static final String ALGORITHM = "RSA";

    public static String encryptWithPublicKey(String data, String publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, KeyFactory.getInstance(ALGORITHM).generatePublic(new X509EncodedKeySpec(Base64.getDecoder().decode(publicKey))));
        byte[] encryptedBytes = cipher.doFinal(data.getBytes());
        return Base64.getEncoder().encodeToString(encryptedBytes);
    }

    public static String decryptWithPrivateKey(String encryptedData, String privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, KeyFactory.getInstance(ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(Base64.getDecoder().decode(privateKey))));
        byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(encryptedData));
        return new String(decryptedBytes);
    }

    public static void generateKeyPair() throws Exception {
        try {
            // 初始化KeyPairGenerator对象，‌并设置密钥对的算法
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
            // 初始化密钥对的生成，‌设置密钥大小为2048位
            keyPairGenerator.initialize(2048);
            // 生成密钥对
            KeyPair keyPair = keyPairGenerator.generateKeyPair();
            // 获取公钥
            PublicKey publicKey = keyPair.getPublic();
            // 获取私钥
            PrivateKey privateKey = keyPair.getPrivate();

            // 打印公钥和私钥
            System.out.println("Public Key: " + Base64.getEncoder().encodeToString(publicKey.getEncoded()));
            System.out.println("Private Key: " + Base64.getEncoder().encodeToString(privateKey.getEncoded()));
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws Exception {
        //generateKeyPair();
        String publicKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAjVxl+xGBFVo5Y8UESbtdPk1HmY8M2u6B9OEbTYVmaPu7jOLBrcthEy4twr9zfJ36/wB9DCrnPng6NU1ZICD7fIn4/ni8OwyPaXSsiF3KZGx/KXK2PgMeMq/Bor+4gH4C5OZVZc2+ocdi0lK4mzab593bwibmFBwGmgdt1Rn1c+dEr3pD3t47OnxSMcPjQlqQjWD90bxyOWqZGf0WxNxTMTClgPEzJMbjGKlwMtHGxsxwruXeuwfVZALn1/TdcuF1DwYQOR0Qak4OuYgTIKv5puQIhG/EF68ZiRhEwzj1eOn8bm0ThLXX/wuBdrlSwbXsrFzS60wuWJ19DvmeUYWF+wIDAQAB";
        String privateKey = "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";

        String encrypt = encryptWithPublicKey("test测试。。。", publicKey);
        System.out.println(encrypt);
        String decrypt = decryptWithPrivateKey(encrypt, privateKey);
        System.out.println(decrypt);
    }
}

3. 使用MessageDigest生成哈希值

package org.example.Test05;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Hashing {
    public static String generateSHA256Hash(String data) throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        md.update(data.getBytes());
        byte[] digest = md.digest();
        return bytesToHex(digest);
    }

    private static String bytesToHex(byte[] bytes) {
        StringBuilder hexString = new StringBuilder();
        for (byte b : bytes) {
            String hex = Integer.toHexString(0xff & b);
            if (hex.length() == 1) hexString.append('0');
            hexString.append(hex);
        }
        return hexString.toString();
    }

    public static void main(String[] args) throws NoSuchAlgorithmException {
        System.out.println(generateSHA256Hash("123"));
    }
}