Virgil Pythia .NET/C# SDK

Introduction | SDK Features | Install and configure SDK | Usage Examples | Docs | Support

Introduction

Virgil Security provides an SDK which allows you to communicate with Virgil Pythia Service and implement Pythia protocol for the following use cases:

• Breach-proof password. Pythia is a technology that gives you a new, more secure mechanism that "breach-proofs" user passwords and lessens the security risks associated with weak passwords by providing cryptographic leverage for the defender (by eliminating offline password cracking attacks), detection for online attacks, and key rotation to recover from stolen password databases.
• BrainKey. User's Private Key which is based on user's password. BrainKey can be easily restored and is resistant to online and offline attacks.

In both cases you get the mechanism which assures you that neither Virgil nor attackers know anything about user's password.

SDK Features

• communicate with Virgil Pythia Service
• manage your Pythia application credentials
• create, verify and update user's breach-proof password
• generate user's BrainKey
• use Virgil Crypto Pythia library

Install and configure SDK

The Virgil .NET Pythia SDK is provided as a package named Virgil.Pythia. The package is distributed via NuGet package management system.

The package is available for .NET Framework 4.5 and newer.

Supported platforms:

• .Net Core 2.0 (MacOS, Linux)

Install SDK Package

Installing the package using Package Manager Console:

Run PM> Install-Package Virgil.Pythia -Version 0.2.0

Configure SDK

When you create a Pythia Application on the Virgil Dashboard you will receive Application credentials including: Proof Key and App ID. Specify your Pythia Application and Virgil account credentials in a Pythia SDK class instance. These credentials are used for the following purposes:

• generating a JWT token that is used for authorization on the Virgil Services
• creating a user's breach-proof password

Here is an example of how to specify your credentials SDK class instance:

// here set your Virgil Account and Pythia Application credentials
var config = new PythiaProtocolConfig
{
    AppId     = "APP_ID",
    ApiKeyId  = "API_KEY_ID",
    ApiKey    = "API_KEY",
    ProofKeys = new[] {
        "PK.1.PROOF_KEY"
    }
};

var pythia = PythiaProtocol.Initialize(config);

Usage Examples

Breach-proof password

Virgil Pythia SDK lets you easily perform all the necessary operations to create, verify and update user's breach-proof password without requiring any additional actions and use Virgil Crypto library.

First of all, you need to set up your database to store users' breach-proof passwords. Create additional columns in your database for storing the following parameters:

Parameters	Type	Size (bytes)	Description
salt	blob	32	Unique random string that is generated by Pythia SDK for each user
deblindedPassword	blob	384	user's breach-proof password
version	int	4	Version of your Pythia Application credentials. This parameter has the same value for all users unless you generate new Pythia credentials on Virgil Dashboard

Now we can start creating breach-proof passwords for users. Depending on the situation, you will use one of the following Pythia SDK functions:

• CreateBreachProofPassword is used to create a user's breach-proof password on your Application Server.
• VerifyBreachProofPassword is used to verify a user's breach-proof password.

Create Breach-Proof Password

Use this flow to create a new breach-proof password for a user.

Remember, if you already have a database with user passwords, you don't have to wait until a user logs in into your system to implement Pythia. You can go through your database and create breach-proof user passwords at any time.

So, in order to create a user's breach-proof password for a new database or available one, go through the following operations:

• Take a user's password (or its hash or whatever you use) and pass it into a CreateBreachProofPassword function in SDK on your Server side.
• Pythia SDK generates unique user's salt and version (which is the same for every user until you change your app credentials on Pythia Service). You need to store user's salt and version in your database in associated columns created on previous step.
• Pythia SDK blinds a password and sends a request to Pythia Service to get a transformed blinded password.
• Pythia SDK de-blinds the transformed blinded password into a user's deblinded password (that we call breach-proof password).

// create a new Breach-proof password using user's password or its hash
var pwd = await pythia.CreateBreachProofPasswordAsync("USER_PASSWORD");

// save Breach-proof password parameters into your users DB

After performing CreateBreachProofPassword function you get previously mentioned parameters (Salt, deblindedPassword, version), save these parameters into corresponding columns in your database.

Check that you updated all database records and delete the now unnecessary column where user passwords were previously stored.

Verify Breach-Proof Password

Use this flow when a user already has his or her own breach-proof password in your database. You will have to pass his or her password into an VerifyBreachProofPassword function:

// get user's Breach-proof password parameters from your users DB

...
// calculate user's Breach-proof password parameters
// compare these parameters with parameters from your DB
var isValid = pythia.VerifyBreachProofPasswordAsync("USER_PASSWORD", pwd);

if (!isValid) 
{
    throw new Exception("Authentication failed");
}

The difference between the VerifyBreachProofPassword and CreateBreachProofPassword functions is that the verification of Pythia Service is optional in VerifyBreachProofPassword function, which allows you to achieve maximum performance when processing data. You can turn on a proof step in VerifyBreachProofPassword function if you have any suspicions that a user or Pythia Service were compromised.

Update breach-proof passwords

This step will allow you to use an updateToken in order to update users' breach-proof passwords in your database.

Use this flow only if your database was COMPROMISED.

How it works:

• Access your Virgil Dashboard and press the "My Database Was Compromised" button.
• Pythia Service generates a special updateToken and new Proof Key.
• You then specify new Pythia Application credentials in the Pythia SDK on your Server side.
• Then you use UpdateBreachProofPassword function to create new breach-proof passwords for your users (you don't need to regenerate user's password).
• Finally, you save the new breach-proof passwords into your database.

Here is an example of using the UpdateBreachProofPassword function:

// get previous user's VerifyBreachProofPassword parameters from a compromised DB

...

// set up an updateToken that you got on the Virgil Dashboard
// update previous user's Breach-proof password, and save new one into your DB

var updatedPwd = pythia.UpdateBreachProofPassword("UT.1.2.UPDATE_TOKEN", pwd);

BrainKey

PYTHIA Service can be used directly as a means to generate strong cryptographic keys based on user's password. We call these keys the BrainKeys. Thus when you need to restore a Private Key you use only user's Password and Pythia Service.

Generate BrainKey

Use this flow to generate a new BrainKey for a user.

In order to create a user's BrainKey, go through the following operations:

• Register your E2EE application on Virgil Dashboard and get your app credentials
• Generate your API key or use available
• Set up JWT provider using previously mentioned parameters (App ID, API key, API key ID) on the Server side
• Generate JWT token with user's identity inside and transmit it to Client side (user's side)
• On Client side set up access token provider in order to specify JWT provider
• Setup BrainKey function with access token provider and pass user's password
• Send BrainKey request to Pythia Service
• Generate keypair based on BrainKey that you've got from Pythia Service and create user's Card
• Pass user's Card to cardManager
• Publish user's Card that is related to the BrainKey

// Define a callback that obtains an Access Token from 
// your application backend service.
Func<TokenContext, Task<string>> tokenCallback = async (ctx) =>
{
    // Getting an Access Token may look like this:
    
    HttpClient client = new HttpClient();
    var responseMessage = await client.GetAsync("https://yourapplication.net/get-virgil-access-token");
    var accessToken = await responseMessage.Content.ReadAsStringAsync();

    return accessToken;
};

// Initialize and create an instace of BrainKey class.
var brainKey = BrainKey.Initialize(tokenCallback);

// Generate default public/private key pair which is Curve ED25519
var keyPair = brainKey.GenerateKeyPair("some password");

Docs

Virgil Security has a powerful set of APIs, and the documentation below can get you started today.

• Breach-Proof Password Use Case
• The Pythia PRF Service - foundation principles of the protocol
• Virgil Security Documentation

License

This library is released under the 3-clause BSD License.

Support

Our developer support team is here to help you. Find out more information on our Help Center.

You can find us on Twitter or send us email support@VirgilSecurity.com.

Also, get extra help from our support team on Slack.