public class EncryptionAndSignatureExample {

public static void main(String[] args) throws Exception {// 生成公私钥对KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");keyPairGenerator.initialize(1024);KeyPair keyPair = keyPairGenerator.generateKeyPair();PrivateKey privateKey = keyPair.getPrivate();PublicKey publicKey = keyPair.getPublic();System.out.println("公钥：" + publicKey);System.out.println("私钥：" + privateKey);// 私钥加密、公钥验签示例String message = "Test message for signature";byte[] signature = sign(privateKey, message);boolean isVerified = verify(publicKey, message, signature);System.out.println("私钥加密、公钥验签结果: " + isVerified);// 公钥加密、私钥解密示例String encryptedMessage = encrypt(publicKey, "Secret message");String decryptedMessage = decrypt(privateKey, encryptedMessage);System.out.println("公钥加密、私钥解密后的消息: " + decryptedMessage);
}public static byte[] sign(PrivateKey privateKey, String message) throws Exception {Signature signature = Signature.getInstance("SHA256withRSA");signature.initSign(privateKey);signature.update(message.getBytes());return signature.sign();
}public static boolean verify(PublicKey publicKey, String message, byte[] signature) throws Exception {Signature verification = Signature.getInstance("SHA256withRSA");verification.initVerify(publicKey);verification.update(message.getBytes());return verification.verify(signature);
}public static String encrypt(PublicKey publicKey, String message) throws Exception {// 这里简单模拟加密，实际应用中需使用更完善的加密逻辑return message + "_encrypted";
}public static String decrypt(PrivateKey privateKey, String encryptedMessage) throws Exception {// 这里简单模拟解密，实际应用中需使用更完善的解密逻辑return encryptedMessage.replace("_encrypted", "");
}

}