Showing posts with label Certification. Show all posts
Showing posts with label Certification. Show all posts

Wednesday, May 24, 2017

How to sign string as well sign request body with public key using Java

Below is a code snippet which will sign your request using Public key.


package com.pkm.src;

import Base64OutputStream;
import IOUtil;

import javax.crypto.Cipher;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.security.MessageDigest;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

/**
 * Created by pritom on 24/05/2017.
 */
public class SignatureSigner {
    public static void main(String[] args) throws Exception {
        String certificateFile = ".....\\publickey.cer";
        String requestBody = "Param1=Value_Of_Param1&Param2=Value_Of_param2";
        String signature = encodeRSASHA1(certificateFile, requestBody);
        System.out.println("Signature=" + signature);
    }

    protected static String encodeRSASHA1(String certificateFile, String requestBody) throws Exception {
        FileInputStream certIn1 = new FileInputStream(certificateFile);
        CertificateFactory e = CertificateFactory.getInstance("X509");
        X509Certificate myCertificate = (X509Certificate) e.generateCertificate(certIn1);

        MessageDigest hashGen = MessageDigest.getInstance("SHA1");
        byte[] hash = hashGen.digest(requestBody.getBytes("UTF-8"));
        Cipher rsa = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        rsa.init(1, myCertificate);
        byte[] signature = rsa.doFinal(hash);

        ByteArrayInputStream sigIn = new ByteArrayInputStream(signature);
        ByteArrayOutputStream sigOut = new ByteArrayOutputStream();
        Base64OutputStream base64Out = new Base64OutputStream(sigOut, "");
        IOUtil.copy(sigIn, base64Out);
        base64Out.close();
        return new String(sigOut.toByteArray(), "US-ASCII");
    }
}

Which will output as below:

Signature=7GNccit4cY+rs4t/S0WBv.........+w1rYdiEO8PxuR3SQ=