java国密数字信封加密

Java 中提供了 Bouncy Castle 库来支持国密算法（SM2，SM3，SM4），下面是使用 Bouncy Castle 库进行国密数字信封加密的示例代码：

import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.engines.SM4Engine;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.crypto.params.ParametersWithRandom;
import org.bouncycastle.crypto.params.SM2EncryptedKeyParameters;
import org.bouncycastle.crypto.params.SM2KeyExchangePrivateParameters;
import org.bouncycastle.crypto.params.SM2KeyExchangePublicParameters;
import org.bouncycastle.crypto.util.PrivateKeyFactory;
import org.bouncycastle.crypto.util.PublicKeyFactory;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.encoders.Base64;

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.Security;
import java.util.Arrays;

public class SM2EnvelopeEncryptionDemo {

    // 加密算法的名称
    private static final String ENCRYPTION_ALGORITHM_NAME = "SM2";

    // 对称加密算法的名称
    private static final String SYMMETRIC_ENCRYPTION_ALGORITHM_NAME = "SM4/ECB/PKCS7Padding";

    // 对称加密算法的密钥长度
    private static final int SYMMETRIC_ENCRYPTION_KEY_SIZE = 128;

    public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());

        // 生成 SM2 密钥对
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ENCRYPTION_ALGORITHM_NAME, "BC");
        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        // 获取公钥和私钥
        AsymmetricKeyParameter publicKey = PublicKeyFactory.createKey(keyPair.getPublic().getEncoded());
        AsymmetricKeyParameter privateKey = PrivateKeyFactory.createKey(keyPair.getPrivate().getEncoded());

        // 生成对称加密算法的密钥
        byte[] symmetricKey = new byte[SYMMETRIC_ENCRYPTION_KEY_SIZE / 8];
        SecureRandom random = new SecureRandom();
        random.nextBytes(symmetricKey);

        // 构造数字信封
        SM2KeyExchangePublicParameters senderPublicKeyParams = new SM2KeyExchangePublicParameters(publicKey);
        SM2KeyExchangePrivateParameters receiverPrivateKeyParams = new SM2KeyExchangePrivateParameters(privateKey);
        SM2KeyExchangePublicParameters receiverPublicKeyParams = senderPublicKeyParams;
        SM2KeyExchangePrivateParameters senderPrivateKeyParams = receiverPrivateKeyParams;
        SM2KeyExchange.SM2KeyExchangeResult keyExchangeResult = SM2KeyExchange.computeKeyExchange(senderPrivateKeyParams, senderPublicKeyParams, receiverPrivateKeyParams, receiverPublicKeyParams);
        SM2EncryptedKeyParameters encryptedKeyParams = new SM2EncryptedKeyParameters(keyExchangeResult.encryptedKey, keyExchangeResult.ephemeralPublicKey);

        // 加密数据
        SM4Engine sm4Engine = new SM4Engine();
        sm4Engine.init(true, new KeyParameter(symmetricKey));
        byte[] encryptedData = new byte[sm4Engine.getOutputSize(plainText.length)];
        int outputLen = sm4Engine.processBytes(plainText, 0, plainText.length, encryptedData, 0);
        outputLen += sm4Engine.doFinal(encryptedData, outputLen);

        // 拼接密文
        byte[] encryptedKey = encryptedKeyParams.getEncryptedKey();
        byte[] iv = encryptedKeyParams.getIv();
        byte[] cipherText = encryptedData;
        byte[] encryptedMessage = new byte[encryptedKey.length + iv.length + cipherText.length];
        System.arraycopy(encryptedKey, 0, encryptedMessage, 0, encryptedKey.length);
        System.arraycopy(iv, 0, encryptedMessage, encryptedKey.length, iv.length);
        System.arraycopy(cipherText, 0, encryptedMessage, encryptedKey.length + iv.length, cipherText.length);

        // 输出结果
        System.out.println("Symmetric Key (Base64): " + Base64.toBase64String(symmetricKey));
        System.out.println("Encrypted Message (Base64): " + Base64.toBase64String(encryptedMessage));
    }
}

在这个示例代码中，首先使用 Bouncy Castle 库生成了一个 SM2 密钥对，然后生成了对称加密算法（SM4）的密钥，接着构造了数字信封并进行了加密，最后输出了加密后的结果。

需要注意的是，如果要使用 SM2 算法进行数字信封加密，必须使用 SM2 密钥交换算法来加密对称加密算法的密钥，然后再使用对称加密算法加密数据。