java RSA加密算法代码

以下是Java实现RSA加密算法的代码：

import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;
import javax.crypto.Cipher;

public class RSA {
    private static final int KEY_SIZE = 512;

    public static void main(String[] args) throws Exception {
        String plainText = "Hello, RSA!";
        KeyPair keyPair = generateKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();
        byte[] encryptedText = encrypt(plainText.getBytes(), publicKey);
        byte[] decryptedText = decrypt(encryptedText, privateKey);
        System.out.println("Plain text: " + plainText);
        System.out.println("Encrypted text: " + new String(encryptedText));
        System.out.println("Decrypted text: " + new String(decryptedText));
    }

    public static KeyPair generateKeyPair() throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(KEY_SIZE);
        return keyPairGenerator.generateKeyPair();
    }

    public static byte[] encrypt(byte[] input, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(input);
    }

    public static byte[] decrypt(byte[] input, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(input);
    }

    public static PublicKey getPublicKey(byte[] modulusBytes, byte[] exponentBytes) throws Exception {
        BigInteger modulus = new BigInteger(1, modulusBytes);
        BigInteger exponent = new BigInteger(1, exponentBytes);
        RSAPublicKeySpec spec = new RSAPublicKeySpec(modulus, exponent);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        return keyFactory.generatePublic(spec);
    }

    public static PrivateKey getPrivateKey(byte[] modulusBytes, byte[] exponentBytes, byte[] dBytes, byte[] pBytes, byte[] qBytes) throws Exception {
        BigInteger modulus = new BigInteger(1, modulusBytes);
        BigInteger exponent = new BigInteger(1, exponentBytes);
        BigInteger d = new BigInteger(1, dBytes);
        BigInteger p = new BigInteger(1, pBytes);
        BigInteger q = new BigInteger(1, qBytes);
        RSAPrivateKeySpec spec = new RSAPrivateKeySpec(modulus, exponent);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = keyFactory.generatePrivate(spec);
        RSAPrivateCrtKeySpec crtSpec = new RSAPrivateCrtKeySpec(modulus, exponent, d, p, q, null, null, null);
        return keyFactory.generatePrivate(crtSpec);
    }
}

在main方法中，我们首先生成了一个密钥对（公钥和私钥），然后使用公钥加密了一段明文，再使用私钥解密得到了原文。其中，使用了Java内置的RSA加密算法实现，通过调用Cipher类的init和doFinal方法实现加解密。同时，我们还提供了getPublicKey和getPrivateKey方法，用于根据给定的参数构造PublicKey和PrivateKey对象。