The section describes how the RSA signature sent in the callback header can be verified. The signature is generated using an RSA Signing. For verification to succeed, the public key is required.
Obtain the Public Key - Based on environment
Copy the public key for the environment you're working with from here. This document assumes that the public key would be stored somewhere on your server under the name ellypay.public.key.pem
Next Steps
Below is the sample callback data for this demonstration
Form the string payload to be used in signature verification. This is obtained by concatenating values of the callback data in the format; event:merchant_reference:internal_reference:transaction_type:transaction_status and these values are obtained from the callback data. The string payload in this case would therefore be transaction.charges:MCTREFNGKLP5VQCQSBH2:ELPREFA65BGTFR7NGUXM:COLLECTION:PENDING
Use the public key obtained above to verify the signature as described in the sample source codes below;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.Signature;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
public class SignatureVerifier {
public boolean isValidSignature() throws Exception {
// Read public key from file
Path pathToFile = Paths.get("path-to-file/ellypay.public.key.pem");
byte[] keyBytes = Files.readAllBytes(pathToFile);
// Decode public key
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey publicKey = keyFactory.generatePublic(keySpec);
// Signature and payload
String strPayload = "transaction.charges:MCTREFNGKLP5VQCQSBH2:ELPREFA65BGTFR7NGUXM:COLLECTION:PENDING";
byte[] signatureBytes = Base64.getDecoder().decode("value-of-rsa-signature");
// Verify signature
Signature signature = Signature.getInstance("SHA256withRSA");
signature.initVerify(publicKey);
signature.update(strPayload.getBytes());
return signature.verify(signatureBytes);
}
public static void main(String[] args) throws Exception {
SignatureVerifier verifier = new SignatureVerifier();
System.out.println(verifier.isValidSignature());
}
}
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
public class SignatureVerifier
{
public bool IsValidSignature()
{
// Read public key from file
string pathToFile = @"path-to-file\ellypay.public.key.pem";
string keyContent = File.ReadAllText(pathToFile);
// Decode public key
RSA rsa = RSA.Create();
rsa.ImportFromPem(keyContent);
// Signature and payload
string strPayload = "transaction.charges:MCTREFNGKLP5VQCQSBH2:ELPREFA65BGTFR7NGUXM:COLLECTION:PENDING";
byte[] signatureBytes = Convert.FromBase64String("value-of-rsa-signature");
// Verify signature
var verifier = new RSAPKCS1SignatureDeformatter(rsa);
verifier.SetHashAlgorithm("SHA256");
byte[] payloadBytes = Encoding.UTF8.GetBytes(strPayload);
byte[] sha256Hash;
using (SHA256 sha256 = SHA256.Create())
{
sha256Hash = sha256.ComputeHash(payloadBytes);
}
return verifier.VerifySignature(sha256Hash, signatureBytes);
}
public static void Main(string[] args)
{
SignatureVerifier verifier = new SignatureVerifier();
Console.WriteLine(verifier.IsValidSignature());
}
}
import base64
import hashlib
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives.serialization import load_pem_public_key
def is_valid_signature():
# Read public key from file
with open("path-to-file/ellypay.public.key.pem", "rb") as key_file:
key_content = key_file.read()
# Decode public key
public_key = load_pem_public_key(key_content, backend=default_backend())
# Signature and payload
str_payload = "transaction.charges:MCTREFNGKLP5VQCQSBH2:ELPREFA65BGTFR7NGUXM:COLLECTION:PENDING"
signature_bytes = base64.b64decode("value-of-rsa-signature")
# Verify signature
verifier = public_key.verifier(
signature_bytes,
padding.PKCS1v15(),
hashlib.sha256
)
verifier.update(str_payload.encode())
try:
verifier.verify()
return True
except Exception as e:
print("Signature verification failed:", e)
return False
require 'openssl'
require 'base64'
def is_valid_signature
# Read public key from file
file = File.read("path-to-file/ellypay.public.key.pem")
# Decode public key
public_key = OpenSSL::PKey::RSA.new(file)
# Signature and payload
str_payload = "transaction.charges:MCTREFNGKLP5VQCQSBH2:ELPREFA65BGTFR7NGUXM:COLLECTION:PENDING"
signature_bytes = Base64.decode64("value-of-rsa-signature")
# Verify signature
sha256 = OpenSSL::Digest::SHA256.new
result = public_key.verify(sha256, signature_bytes, str_payload)
result
end
Below is an example of a generated RSA signature (rsa-signature) on the sandbox environment. Feel free to verify it using the sample payload above and the public key.