Edwards

Edwards is a crypto library for Edwards-curve Digital Signature Algorithm (EdDSA). This library makes it easy to create KeyPair, sign and verify your message.

How to use

First of all, you should create Edwards object.

Edwards edwards = new Edwards(new Ed25519SchemeProvider(HashAlgorithm.SHA_512));

or if you select KECCAK-512 hash algorithm and Curve25519, just write as below.

Edwards edwards = new Edwards();

KeyPair generation

You can generate KeyPair which contains PrivateKey and PublicKey from Edwards object.

KeyPair keyPair = edwards.generateKeyPair();
PrivateKey privateKey = keyPair.getPrivateKey();
PublicKey publicKey = keyPair.getPublicKey();

PublicKey generation from existing PrivateKey

Of course you can generate PublicKey from existing PrivateKey which is represented in Hex String or byte array.

PrivateKey privateKey = PrivateKey.newInstance("4fd0a24......3415d4ef");
PublicKey publicKey = edwards.derivePublicKey(privateKey);

Signing

KeyPair keyPair = ...;
byte[] data = ...;
Signature signature = edwards.sign(keyPair, data);

Verifying

PublicKey publicKey = ...;
Signature signature = ...;
byte[] data = ...;
boolean isVerified = edwards.verify(publicKey, data, signature);

Built-in Scheme

Edwards supports some schemes.

• Ed25519
• Ed25519ctx
• Ed25519ph
• Ed448
• Ed448ph

Ed25591ctx, Ed25519ph are contextualized extensions of the Ed25519 scheme, and also Ed448ph is a contextualized extension of Ed448 scheme.

In addition, NemV1SchemeProvider and NemV2SchemeProvider are implemented. The use case of this provider is some operation in NEM v1 and v2 respectively.

Built-in Hash algorithm

This library use SpongyCastle internally, so you can almost all hash algorithm. Specify hash algorithm you want like this.

SchemeProvider schemeProvider = new Ed25519SchemeProvider(HashAlgorithm.SHA_512);

or

Edwards edwards = new Edwards(HashAlgorithm.KECCAK_512);

other algorithm here.

• SHA512
• SHA3-512
• KECCAK-512
• SHAKE-256

If you want to add other hash algorithms, do not hesitate to send me request, or pull request.

Install

A package of this software is provided from jcenter. Maven or Gradle may be useful. Just write as below.

Gradle

buildscript {
    repositories {
        mavenCentral()
    }
}

dependencies {
    compile "io.moatwel.crypto:eddsa:0.8.1"
}

Maven

<dependency> 
    <groupId>io.moatwel.crypto</groupId> 
    <artifactId>eddsa</artifactId> 
    <version>0.8.1</version>
    <type>pom</type> 
</dependency>

How to build

Please use AndroidStudio or Intellij. Clone this repository, and open it.

Dependencies

This software is built on some Open Source Softwares.

• Spongy Castle

License

This software is under the Apache License, Version 2.0.

Copyright 2018 halu5071 (Yasunori Horii)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.