常用的国密算法包含SM2，SM3，SM4。以下针对每个算法使用场景进行说明以比较其差异
- SM2：非对称加密算法，可以替代RSA
- 数字签名，SM2为非对称加密，加解密使用一对私钥和公钥，只有签名发行者拥有私钥，可用于加密，其他需要验证解密或验签者使用公钥进行。如果使用公钥可以成功解密，则可以确定数据、文档或其他数字资产的拥有者。
- 因性能问题，根据实际需要常用于小体积数据加密，例如对密钥或SM3生成的hash进行加密。针对SM3生成的hash值进行加密也是一种常用的签名方式，一般先对需要签名的数据、文档或数字资产使用SM3生成hash再用SM2进行签名。
注：
如果用于加密，那么加密是用公钥进行的，解密是用私钥进行的。
如果用于数字签名，那么签名是用私钥进行的，验证签名则使用公钥。
- SM3：散列哈希算法
- 数据库中用户密码的保存，获取用户输入明文密码后，进行SM3生成hash值，再与数据库中保存的已经过SM3计算后的密码值进行比对。
- 数据完整性验证，针对数据、文件或数据资产进行SM3生成hash并保存，在需要验证数据是否被修改时重新生成hash并与之前保存的hash值进行比对，一旦文件有被修改则会生成不同的hash值。例如可以针对数据库中关键数据字段进行hash，并保存。然后可以通过遍历定期验证hash是否一致，来发现被篡改的数据。
- SM4：对称加密算法，性能比SM2好
- 可以用于一般数据的加密与解密，例如可以在需要网络传输的数据发送前进行加密，对方收到数据后使用相同密钥进行解密获得明文。
基于Java的SM4（ECB模式，CBC模式）对称加解密实现
简单说明：加密算法依赖了groupId:org.bouncycastle中的bcprov-jdk15to18，Bouncy Castle (bcprov-jdk15to18)提供了JDK 1.5 to 1.8可使用的大量标准加密算法实现，其中包含了SM2，SM3，SM4。在这个类库基础上实现了一个SM4Util加解密工具类。注意： 此版本我在JDK1.8环境下，不同版本JDK需要找到匹配的依赖版本1.8及以上可以使用bcprov-jdk18on。Bouncy Castle同时也提供了bcutil-jdk15to18可以实现SM4加解密。
方式一：依赖bcprov-jdk15to18（以ECB模式为例）
<dependency><groupId>org.bouncycastle</groupId><artifactId>bcprov-jdk15to18</artifactId><version>1.77</version>
</dependency>import java.nio.charset.StandardCharsets;
import java.security.Key;
import java.security.MessageDigest;
import java.security.SecureRandom;
import java.security.Security;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.spec.SecretKeySpec;
import org.bouncycastle.jce.provider.BouncyCastleProvider;public class Sm4Utils {static {Security.addProvider(new BouncyCastleProvider());}private static final String ENCODING = "UTF-8";public static final String ALGORIGTHM_NAME = "SM4";public static final String ALGORITHM_NAME_ECB_PADDING = "SM4/ECB/PKCS7Padding";public static final int DEFAULT_KEY_SIZE = 128;private static Cipher generateEcbCipher(String algorithmName, int mode, byte[] key) throws Exception {Cipher cipher = Cipher.getInstance(algorithmName, "BC");Key sm4Key = new SecretKeySpec(key, ALGORIGTHM_NAME);cipher.init(mode, sm4Key);return cipher;}public static byte[] generateKey(String keyString) throws Exception {// Use SHA-256 to hash the string and then take first 128 bits (16 bytes)MessageDigest digest = MessageDigest.getInstance("SHA-256");byte[] hash = digest.digest(keyString.getBytes(StandardCharsets.UTF_8));byte[] key = new byte[16];System.arraycopy(hash, 0, key, 0, 16);return key;}public static String encryptEcb(String key, String paramStr, String charset) throws Exception {String cipherText = "";if (null != paramStr && !"".equals(paramStr)) {byte[] keyData = generateKey(key);charset = charset.trim();if (charset.length() <= 0) {charset = ENCODING;}byte[] srcData = paramStr.getBytes(charset);byte[] cipherArray = encryptEcbPadding(keyData, srcData);cipherText = ByteUtils.toHexString(cipherArray);}return cipherText;}public static byte[] encryptEcbPadding(byte[] key, byte[] data) throws Exception {Cipher cipher = generateEcbCipher("SM4/ECB/PKCS7Padding", Cipher.ENCRYPT_MODE, key);byte[] bs = cipher.doFinal(data);return bs;}public static String decryptEcb(String key, String cipherText, String charset) throws Exception {String decryptStr = "";byte[] keyData = generateKey(key);byte[] cipherData = ByteUtils.fromHexString(cipherText);byte[] srcData = decryptEcbPadding(keyData, cipherData);charset = charset.trim();if (charset.length() <= 0) {charset = ENCODING;}decryptStr = new String(srcData, charset);return decryptStr;}public static byte[] decryptEcbPadding(byte[] key, byte[] cipherText) throws Exception {Cipher cipher = generateEcbCipher("SM4/ECB/PKCS7Padding", Cipher.DECRYPT_MODE, key);return cipher.doFinal(cipherText);}public static void main(String[] args) {try {String json = "311111190001010001";String key = "test";String cipher = encryptEcb(key, json, ENCODING);System.out.println(cipher);System.out.println(decryptEcb(key, cipher, ENCODING));} catch (Exception var5) {var5.printStackTrace();}}
}方式二：依赖bcprov-jdk15to18（以CBC模式为例），代码根据GPT-4生成修改调试，可运行。
<dependency><groupId>org.bouncycastle</groupId><artifactId>bcprov-jdk15to18</artifactId><version>1.77</version>
</dependency>
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.engines.SM4Engine;
import org.bouncycastle.crypto.modes.CBCBlockCipher;
import org.bouncycastle.crypto.modes.CBCModeCipher;
import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.jce.provider.BouncyCastleProvider;import java.security.Security;
import java.util.Arrays;public class SM4Example {static {Security.addProvider(new BouncyCastleProvider());}public static byte[] encrypt(byte[] key, byte[] iv, byte[] data) throws Exception {SM4Engine engine = new SM4Engine();CBCModeCipher cbcBlockCipher = CBCBlockCipher.newInstance(engine);PaddedBufferedBlockCipher cipher = new PaddedBufferedBlockCipher(cbcBlockCipher);CipherParameters params = new ParametersWithIV(new KeyParameter(key), iv);cipher.init(true, params);byte[] temp = new byte[cipher.getOutputSize(data.length)];int len = cipher.processBytes(data, 0, data.length, temp, 0);len += cipher.doFinal(temp, len);byte[] out = new byte[len];System.arraycopy(temp, 0, out, 0, len);return out;}public static byte[] decrypt(byte[] key, byte[] iv, byte[] data) throws Exception {SM4Engine engine = new SM4Engine();CBCModeCipher cbcBlockCipher = CBCBlockCipher.newInstance(engine);PaddedBufferedBlockCipher cipher = new PaddedBufferedBlockCipher(cbcBlockCipher);CipherParameters params = new ParametersWithIV(new KeyParameter(key), iv);cipher.init(false, params);byte[] temp = new byte[cipher.getOutputSize(data.length)];int len = cipher.processBytes(data, 0, data.length, temp, 0);len += cipher.doFinal(temp, len);byte[] out = new byte[len];System.arraycopy(temp, 0, out, 0, len);return out;}public static void main(String[] args) throws Exception {byte[] key = "0123456789abcdef".getBytes(); // 16-byte key for SM4byte[] iv = "abcdef9876543210".getBytes(); // 16-byte IV for CBC modebyte[] dataToEncrypt = "Hello, Bouncy Castle SM4!".getBytes();byte[] encryptedData = encrypt(key, iv, dataToEncrypt);System.out.println("Encrypted Data: " + java.util.Base64.getEncoder().encodeToString(encryptedData));byte[] decryptedData = decrypt(key, iv, encryptedData);System.out.println("Decrypted Data: " + new String(decryptedData));}
}
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