項目涉及保密傳輸，要求使用國密算法，一般遇到類似問題首先想到的就是使用非對稱加密，後端生成密鑰對，將公鑰交給前端，前端用公鑰加密數據，後端用私鑰對數據解密。項目的複雜度在於國密的非對稱加密算法SM2的Java及JS實現。
Java版比較好辦，較新版本的bouncycastle就支持了SM2/SM3/SM4，麻煩在於JS版，找了很多都有問題，直到遇到了這個項目：https://github.com/Saberization/SM2，感謝作者。分別整理下前端後端的實現過程：
後端首先引入bouncycastle，Maven配置如下：
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15on</artifactId>
<version>1.65</version>
</dependency>
後端Java代碼如下：
//生成密鑰對
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();
//私鑰，16進制格式，自己保存，格式如a2081b5b81fbea0b6b973a3ab6dbbbc65b1164488bf22d8ae2ff0b8260f64853
BigInteger privatekey = ((ECPrivateKeyParameters) asymmetricCipherKeyPair.getPrivate()).getD();
String privateKeyHex = privatekey.toString(16);
//公鑰，16進制格式，發給前端，格式如04813d4d97ad31bd9d18d785f337f683233099d5abed09cb397152d50ac28cc0ba43711960e811d90453db5f5a9518d660858a8d0c57e359a8bf83427760ebcbba
ECPoint ecPoint = ((ECPublicKeyParameters) asymmetricCipherKeyPair.getPublic()).getQ();
String publicKeyHex = Hex.toHexString(ecPoint.getEncoded(false));
前端Javascript示例代碼，寫了個頁面：
<!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() {
//公鑰，16進制格式，由後端生成
var pubkeyHex = "04813d4d97ad31bd9d18d785f337f683233099d5abed09cb397152d50ac28cc0ba43711960e811d90453db5f5a9518d660858a8d0c57e359a8bf83427760ebcbba";
var encryptData = sm2Encrypt("SM2 Encryption Test", pubkeyHex, 0);
console.log(encryptData);
}
</script>
</head>
<body onload="encrypt()">
</body>
</html>
執行會生成密文，每次生成都會不同，比如我的環境某次生成如下：
04be17bf6fe47da1f34a01ad0ff67901241b72d103e998f2f7cc78a004703bdfb8d2c6e3939f4f708f3a57d872d58ec5c41bbe5976666bcb01acea43f5a1c68a62cc117c24821d17c3023035641894d7c978a5521f8dc6798515550c73071f9703602e0ee490157729b648c1cc3eb929c1a0501e12a216d42461117402
後端嘗試解密：
//JS加密產生的密文
String cipherData = "04be17bf6fe47da1f34a01ad0ff67901241b72d103e998f2f7cc78a004703bdfb8d2c6e3939f4f708f3a57d872d58ec5c41bbe5976666bcb01acea43f5a1c68a62cc117c24821d17c3023035641894d7c978a5521f8dc6798515550c73071f9703602e0ee490157729b648c1cc3eb929c1a0501e12a216d42461117402";
byte[] cipherDataByte = Hex.decode(cipherData);
//剛纔的私鑰Hex，先還原私鑰
String privateKey = "a2081b5b81fbea0b6b973a3ab6dbbbc65b1164488bf22d8ae2ff0b8260f64853";
BigInteger privateKeyD = new BigInteger(privateKey, 16);
ECPrivateKeyParameters privateKeyParameters = new ECPrivateKeyParameters(privateKeyD, domainParameters);
//用私鑰解密
SM2Engine sm2Engine = new SM2Engine();
sm2Engine.init(false, privateKeyParameters);
//processBlock得到Base64格式，記得解碼
byte[] arrayOfBytes = Base64.getDecoder().decode(sm2Engine.processBlock(cipherDataByte, 0, cipherDataByte.length));
//得到明文：SM2 Encryption Test
String data = new String(arrayOfBytes);