2.5 Method of Signature

1.import io.netty.util.CharsetUtil;
2.import org.apache.commons.codec.binary.Base64;
3.import javax.crypto.Cipher;
4.import java.nio.charset.StandardCharsets;
5.import java.security.*;
6.import java.security.spec.PKCS8EncodedKeySpec;
7.import java.security.spec.X509EncodedKeySpec;
8. 
9.public class Demo {
10. 
11.    /**
12.     * For creating signature for an request
13.     *
14.     * @param data   request data, request body e.g."{\"msgId\":\"999\",\"mchId\":\"1234567\", ....}"
15.     * @param priKey the pair of the one (sign pub key) you uploaded, create signed public key uploaded by merchant to correspond the private key 
16.     * @return signature of the request data, you should set it into "signature" field, check our example on document 
17.     */
18.    public static String signBySHA256WithRSA(String data, String priKey) throws Exception {
19.        try {
20.            Signature signature = Signature.getInstance("SHA256WithRSA");
21.            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(priKey));
22.            PrivateKey privateKey = KeyFactory.getInstance("RSA").generatePrivate(keySpec);
23.            signature.initSign(privateKey);
24.            signature.update(data.getBytes("UTF-8"));
25.            return Base64.encodeBase64String(signature.sign());
26.        } catch (Exception e) {
27.            throw new Exception("RSA signature creating error");
28.        }
29.    }
30. 
31. 
32.    /**
33.     * For verifying signature for an request / response 
34.     *
35.     * @param data   all contents in "response" or "request" field, e.g. "response":{"code":"200","message":"Success", ...}
36.     * @param sign   all contents in "signature" field 
37.     * @param pubKey the public signing key provided by Wallyt
38.     * @return true if valid, 
39.     */
40.    public static boolean verifyBySHA256WithRSA(String data, String sign, String pubKey) throws Exception {
41.        try {
42.            Signature signature = Signature.getInstance("SHA256WithRSA");
43.            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(Base64.decodeBase64(pubKey));
44.            PublicKey publicKey = KeyFactory.getInstance("RSA").generatePublic(keySpec);
45.            signature.initVerify(publicKey);
46.            signature.update(data.getBytes(StandardCharsets.UTF_8));
47.            return signature.verify(Base64.decodeBase64(sign.getBytes(StandardCharsets.UTF_8)));
48.        } catch (Exception e) {
49.            throw new Exception("RSA signature verifying error");
50.        }
51.    }
52.}