Java使用RSA加密解密及签名校验

Java中可以使用RSA算法进行加密、解密和签名校验。下面是使用RSA进行加密、解密和签名校验的示例代码：

1. 密钥生成：

   import java.security.KeyPair;
   import java.security.KeyPairGenerator;
   import java.security.NoSuchAlgorithmException;
   import java.security.PrivateKey;
   import java.security.PublicKey;
   
   public class RSAKeyGenerator {
       public static KeyPair generateKeyPair() throws NoSuchAlgorithmException {
           KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
           keyPairGenerator.initialize(2048); // 指定密钥长度为2048位
           return keyPairGenerator.generateKeyPair();
       }
   
       public static void main(String[] args) throws NoSuchAlgorithmException {
           KeyPair keyPair = generateKeyPair();
           PublicKey publicKey = keyPair.getPublic();
           PrivateKey privateKey = keyPair.getPrivate();
   
           System.out.println("Public Key: " + publicKey);
           System.out.println("Private Key: " + privateKey);
       }
   }
   

   运行以上代码，将生成一对RSA公私钥。

2. 加密解密：

   import javax.crypto.Cipher;
   import java.nio.charset.StandardCharsets;
   import java.security.*;
   import java.util.Base64;
   
   public class RSAEncryptDecrypt {
       public static String encrypt(String plainText, PublicKey publicKey) throws Exception {
           Cipher cipher = Cipher.getInstance("RSA");
           cipher.init(Cipher.ENCRYPT_MODE, publicKey);
           byte[] encryptedBytes = cipher.doFinal(plainText.getBytes(StandardCharsets.UTF_8));
           return Base64.getEncoder().encodeToString(encryptedBytes);
       }
   
       public static String decrypt(String encryptedText, PrivateKey privateKey) throws Exception {
           byte[] encryptedBytes = Base64.getDecoder().decode(encryptedText);
           Cipher cipher = Cipher.getInstance("RSA");
           cipher.init(Cipher.DECRYPT_MODE, privateKey);
           byte[] decryptedBytes = cipher.doFinal(encryptedBytes);
           return new String(decryptedBytes, StandardCharsets.UTF_8);
       }
   
       public static void main(String[] args) throws Exception {
           KeyPair keyPair = RSAKeyGenerator.generateKeyPair();
           PublicKey publicKey = keyPair.getPublic();
           PrivateKey privateKey = keyPair.getPrivate();
   
           String plainText = "Hello, RSA!";
           String encryptedText = encrypt(plainText, publicKey);
           String decryptedText = decrypt(encryptedText, privateKey);
   
           System.out.println("Plain Text: " + plainText);
           System.out.println("Encrypted Text: " + encryptedText);
           System.out.println("Decrypted Text: " + decryptedText);
       }
   }
   

   运行以上代码，将输出明文、加密后的密文和解密后的明文。

3. 签名校验：

   import java.nio.charset.StandardCharsets;
   import java.security.*;
   
   public class RSASignatureVerification {
       public static byte[] sign(String plainText, PrivateKey privateKey) throws Exception {
           Signature signature = Signature.getInstance("SHA256withRSA");
           signature.initSign(privateKey);
           signature.update(plainText.getBytes(StandardCharsets.UTF_8));
           return signature.sign();
       }
   
       public static boolean verify(String plainText, byte[] signatureBytes, PublicKey publicKey) throws Exception {
           Signature signature = Signature.getInstance("SHA256withRSA");
           signature.initVerify(publicKey);
           signature.update(plainText.getBytes(StandardCharsets.UTF_8));
           return signature.verify(signatureBytes);
       }
   
       public static void main(String[] args) throws Exception {
           KeyPair keyPair = RSAKeyGenerator.generateKeyPair();
           PublicKey publicKey = keyPair.getPublic();
           PrivateKey privateKey = keyPair.getPrivate();
   
           String plainText = "Hello, RSA!";
           byte[] signature = sign(plainText, privateKey);
           boolean isVerified = verify(plainText, signature, publicKey);
   
           System.out.println("Plain Text: " + plainText);
           System.out.println("Signature: " + Base64.getEncoder().encodeToString(signature));
           System.out.println("Verification Result: " + isVerified);
       }
   }
   

   运行以上代码，将输出明文、签名和校验结果。

以上是使用RSA进行加密解密和签名校验的Java示例代码。请注意，RSA算法需要正确处理密钥的生成、存储和保管，同时保证传输的安全性。