项目涉及保密传输，要求使用国密算法，一般遇到类似问题首先想到的就是使用非对称加密，后端生成密钥对，将公钥交给前端，前端用公钥加密数据，后端用私钥对数据解密。项目的复杂度在于国密的非对称加密算法SM2的Java及JS实现。
Java版比较好办，较新版本的bouncycastle就支持了SM2/SM3/SM4，麻烦在于JS版，找了很多都有问题，直到遇到了这个项目：https://github.com/Saberization/SM2，感谢作者。分别整理下前端后端的实现过程：
后端首先引入bouncycastle，Maven配置如下：
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15on</artifactId>
<version>1.65</version>
</dependency>
后端Java代码如下：
//生成密钥对
X9ECParameters sm2ECParameters = GMNamedCurves.getByName("sm2p256v1");
ECDomainParameters domainParameters = new ECDomainParameters(sm2ECParameters.getCurve(), sm2ECParameters.getG(), sm2ECParameters.getN());
ECKeyPairGenerator keyPairGenerator = new ECKeyPairGenerator();
keyPairGenerator.init(new ECKeyGenerationParameters(domainParameters, SecureRandom.getInstance("SHA1PRNG")));
AsymmetricCipherKeyPair asymmetricCipherKeyPair = keyPairGenerator.generateKeyPair();
//私钥，16进制格式，自己保存，格式如a2081b5b81fbea0b6b973a3ab6dbbbc65b1164488bf22d8ae2ff0b8260f64853
BigInteger privatekey = ((ECPrivateKeyParameters) asymmetricCipherKeyPair.getPrivate()).getD();
String privateKeyHex = privatekey.toString(16);
//公钥，16进制格式，发给前端，格式如04813d4d97ad31bd9d18d785f337f683233099d5abed09cb397152d50ac28cc0ba43711960e811d90453db5f5a9518d660858a8d0c57e359a8bf83427760ebcbba
ECPoint ecPoint = ((ECPublicKeyParameters) asymmetricCipherKeyPair.getPublic()).getQ();
String publicKeyHex = Hex.toHexString(ecPoint.getEncoded(false));
前端Javascript示例代码，写了个页面：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>SM2-TEST</title>
<script src="crypto-js.js"></script>
<script src="sm2.js"></script>
<script>
function encrypt() {
//公钥，16进制格式，由后端生成
var pubkeyHex = "04813d4d97ad31bd9d18d785f337f683233099d5abed09cb397152d50ac28cc0ba43711960e811d90453db5f5a9518d660858a8d0c57e359a8bf83427760ebcbba";
var encryptData = sm2Encrypt("SM2 Encryption Test", pubkeyHex, 0);
console.log(encryptData);
}
</script>
</head>
<body onload="encrypt()">
</body>
</html>
执行会生成密文，每次生成都会不同，比如我的环境某次生成如下：
04be17bf6fe47da1f34a01ad0ff67901241b72d103e998f2f7cc78a004703bdfb8d2c6e3939f4f708f3a57d872d58ec5c41bbe5976666bcb01acea43f5a1c68a62cc117c24821d17c3023035641894d7c978a5521f8dc6798515550c73071f9703602e0ee490157729b648c1cc3eb929c1a0501e12a216d42461117402
后端尝试解密：
//JS加密产生的密文
String cipherData = "04be17bf6fe47da1f34a01ad0ff67901241b72d103e998f2f7cc78a004703bdfb8d2c6e3939f4f708f3a57d872d58ec5c41bbe5976666bcb01acea43f5a1c68a62cc117c24821d17c3023035641894d7c978a5521f8dc6798515550c73071f9703602e0ee490157729b648c1cc3eb929c1a0501e12a216d42461117402";
byte[] cipherDataByte = Hex.decode(cipherData);
//刚才的私钥Hex，先还原私钥
String privateKey = "a2081b5b81fbea0b6b973a3ab6dbbbc65b1164488bf22d8ae2ff0b8260f64853";
BigInteger privateKeyD = new BigInteger(privateKey, 16);
ECPrivateKeyParameters privateKeyParameters = new ECPrivateKeyParameters(privateKeyD, domainParameters);
//用私钥解密
SM2Engine sm2Engine = new SM2Engine();
sm2Engine.init(false, privateKeyParameters);
//processBlock得到Base64格式，记得解码
byte[] arrayOfBytes = Base64.getDecoder().decode(sm2Engine.processBlock(cipherDataByte, 0, cipherDataByte.length));
//得到明文：SM2 Encryption Test
String data = new String(arrayOfBytes);