DigitalSignClientSnippet.java

package org.arttha.fruit.common.crypto;

import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.util.Base64;

public class DigitalSignClientSnippet{

	private static final String SIGNATURE_ALGO = "SHA256withRSA";

	public static void main(String[] args) throws Exception {

		String keystorePath = "arttha_sandbox_passport.jks";
        String keystorePassword = "{kestore_password}";
		String key=KeyStoreUtil.getKeyFromKeyStore(keystorePath,
				keystorePassword, "{alias}", "{key_password}");
		PrivateKey privateKey = getPrivateKeyFromBytes(Base64.getDecoder().decode(key));
		String requestBody = "{" + "\"userIdentification\": \"john waler\"," + "\"deviceid\":\"77881992\"" + "}";
		String encDate = Base64.getEncoder().encodeToString(sign(requestBody, privateKey));
		System.out.println(encDate);
	}

	public static byte[] sign(String requestData, PrivateKey privateKey)
			throws NoSuchAlgorithmException, InvalidKeyException, SignatureException {
		Signature signature = Signature.getInstance(SIGNATURE_ALGO);
		signature.initSign(privateKey);
		signature.update(requestData.getBytes());
		return signature.sign();
	}

	public static PrivateKey getPrivateKeyFromBytes(byte[] privateKeyBytes) throws Exception {
		PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
		return keyFactory.generatePrivate(keySpec);
	}
}