A lightweight and fast ECDSA

Overview

This is a pure Java implementation of the Elliptic Curve Digital Signature Algorithm (ECDSA). It is compatible with Java 8+ and OpenSSL. It uses some elegant math such as Jacobian Coordinates to speed up the ECDSA.

Installation

Maven Central

In pom.xml:

<dependency>
    <groupId>com.starkbank</groupId>
    <artifactId>starkbank-ecdsa</artifactId>
    <version>1.0.2</version>
</dependency>

Then run:

mvn clean install

Curves

We currently support secp256k1, but it's super easy to add more curves to the project. Just add them on Curve.java

Speed

We ran a test on JDK 13.0.1 on a MAC Pro i5 2019. The libraries ran 100 times and showed the average times displayed bellow:

Library	sign	verify
java.security	0.9ms	2.4ms
starkbank-ecdsa	4.3ms	9.9ms

Sample Code

How to use it:

import com.starkbank.ellipticcurve.PrivateKey;
import com.starkbank.ellipticcurve.PublicKey;
import com.starkbank.ellipticcurve.Signature;
import com.starkbank.ellipticcurve.Ecdsa;


public class GenerateKeys{

    public static void main(String[] args){
        // Generate Keys
        PrivateKey privateKey = new PrivateKey();
        PublicKey publicKey = privateKey.publicKey();

        String message = "Testing message";
        // Generate Signature
        Signature signature = Ecdsa.sign(message, privateKey);

        // Verify if signature is valid
        boolean verified = Ecdsa.verify(message, signature, publicKey) ;

        // Return the signature verification status
        System.out.println("Verified: " + verified);

    }
}

OpenSSL

This library is compatible with OpenSSL, so you can use it to generate keys:

openssl ecparam -name secp256k1 -genkey -out privateKey.pem
openssl ec -in privateKey.pem -pubout -out publicKey.pem

Create a message.txt file and sign it:

openssl dgst -sha256 -sign privateKey.pem -out signatureBinary.txt message.txt

It's time to verify:

import com.starkbank.ellipticcurve.Ecdsa;
import com.starkbank.ellipticcurve.PublicKey;
import com.starkbank.ellipticcurve.Signature;
import com.starkbank.ellipticcurve.utils.ByteString;
import com.starkbank.ellipticcurve.utils.File;


public class VerifyKeys {

    public static void main(String[] args){
        // Read files
        String publicKeyPem = File.read("publicKey.pem");
        byte[] signatureBin = File.readBytes("signatureBinary.txt");
        String message = File.read("message.txt");

        ByteString byteString = new ByteString(signatureBin);

        PublicKey publicKey = PublicKey.fromPem(publicKeyPem);
        Signature signature = Signature.fromDer(byteString);

        // Get verification status:
        boolean verified = Ecdsa.verify(message, signature, publicKey);
        System.out.println("Verification status: " + verified);
    }
}

You can also verify it on terminal:

openssl dgst -sha256 -verify publicKey.pem -signature signatureBinary.txt message.txt

NOTE: If you want to create a Digital Signature to use in the Stark Bank, you need to convert the binary signature to base64.

openssl base64 -in signatureBinary.txt -out signatureBase64.txt

You can also verify it with this library:

import com.starkbank.ellipticcurve.utils.ByteString;
import com.starkbank.ellipticcurve.Signature;
import com.starkbank.ellipticcurve.utils.File;


public class GenerateSignature {

    public static void main(String[] args) {
        // Load signature file
        byte[] signatureBin = File.readBytes("signatureBinary.txt");
        Signature signature = Signature.fromDer(new ByteString(signatureBin));
        // Print signature
        System.out.println(signature.toBase64());
        }
}

Run all unit tests

gradle test