Settting Up the Development Environment

Install Java and Maven on OpenEuler:

sudo yum install java-17-openjdk
sudo yum install maven

Creating the Project Srtucture

1. Create a Maven project by adding the following dependencies to pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>CryptoApp</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.bouncycastle</groupId>
            <artifactId>bcprov-jdk15to18</artifactId>
            <version>1.77</version>
        </dependency>
        <dependency>
            <groupId>org.bouncycastle</groupId>
            <artifactId>bcprov-ext-jdk15to18</artifactId>
            <version>1.77</version>
        </dependency>
    </dependencies>
</project>

2. Create the following Java files in src/main/java:

CryptoDemo.java:

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import java.security.Security;

public class CryptoDemo {
    static {
        Security.addProvider(new BouncyCastleProvider());
    }

    public static void main(String[] args) {
        String message = "Sample text for encryption";
        String secretKey = CryptoUtils.generateKey();
        
        String encrypted = new CryptoUtils().encryptData(message, secretKey);
        System.out.println("Encrypted: " + encrypted);
        
        String decrypted = new CryptoUtils().decryptData(encrypted, secretKey);
        System.out.println("Decrypted: " + decrypted);
    }
}

CryptoUtils.java:

import org.bouncycastle.crypto.engines.SM4Engine;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.util.encoders.Hex;
import org.bouncycastle.util.encoders.Base64;
import java.security.SecureRandom;

public class CryptoUtils {
    public static String generateKey() {
        byte[] keyData = new byte[16];
        new SecureRandom().nextBytes(keyData);
        return Base64.toBase64String(keyData);
    }

    public String encryptData(String input, String key) {
        byte[] keyBytes = Base64.decode(key);
        byte[] inputBytes = input.getBytes();
        byte[] output = new byte[inputBytes.length];
        
        SM4Engine cipher = new SM4Engine();
        cipher.init(true, new KeyParameter(keyBytes));
        cipher.processBlock(inputBytes, 0, output, 0);
        
        return Hex.toHexString(output);
    }

    public String decryptData(String encrypted, String key) {
        byte[] keyBytes = Base64.decode(key);
        byte[] inputBytes = Hex.decode(encrypted);
        byte[] output = new byte[inputBytes.length];
        
        SM4Engine cipher = new SM4Engine();
        cipher.init(false, new KeyParameter(keyBytes));
        cipher.processBlock(inputBytes, 0, output, 0);
        
        return new String(output);
    }
}

Building and Running the Application

1. Compile the project:

mvn clean package

2. Execute the application:

java -cp target/classes:target/CryptoApp-1.0-SNAPSHOT.jar CryptoDemo