PJCL – Pomcor

Passwordless Authentication for the Consumer Space

This is part 1 of a series on cryptographic authentication. Part 2 and Part 3 are now available.

FIDO adoption lags in spite of general availability

In a white paper issued in March 2022 the FIDO Alliance candidly announced that FIDO-based authentication based on the FIDO2 standards, which include the Client-To-Authenticator Protocol of the FIDO Alliance and the companion Web Authentication API (WebAuthn) of the W3C “has not attained large-scale adoption in the consumer space”.

FIDO2 is a cryptographic authentication solution for the web, which uses a key pair managed by an authenticator and is advertised by the FIDO Alliance as being “passwordless”. The key pair may be stored in the authenticator, or, equivalently from a security viewpoint, it may be encrypted under a symmetric key stored in the authenticator, and exported to play the role of a “credential ID”. The authenticator may be a “roaming authenticator” carried in a “security key”, or a “platform authenticator” provided by the OS of the user’s smartphone or laptop.

Early authenticators were security keys, which few web users had. Today most smartphones and laptops have platform authenticators, and that makes FIDO2 a generally available web technology. But the announcement by the FIDO Alliance shows that general availability has not translated into general adoption.

The white paper attributes this to challenges that consumers face with platform authenticators: “having to re-enroll each new device”, and having “no easy ways to recover from a lost or stolen device” as the credentials managed by the platform authenticator of the device are lost. To address the loss-of-credential problem, Apple, Google and Microsoft have announced a joint effort to devise solutions that are expected to become available “in the course of the coming year” and that, according to the white paper, will involve “multi-device credentials”.

Another contributing factor to the lack of adoption, however, is no doubt the complexity and cost of the FIDO2 authentication solution. Implementing the solution in a web app requires FIDO Server software provided by a company certified to provide such software by the FIDO Alliance. A team from the certified company must work with a team from the company that is developing the app to integrate the solution into the app. By contrast, an ordinary 2FA solution is implemented by the app developers themselves, possibly by a single developer, without any integration effort.

Thus FIDO faces two obstacles to widespread adoption: usability and cost.

Two working demonstrations of cryptographic authentication on GitHub

But cryptographic authentication need not be complicated, costly or challenging to the consumer. It can be implemented simply by storing a key pair in persistent browser storage (localStorage or IndexDB), registering the public key, and authenticating by proof of possession of the private key. I will refer to this as the browser storage solution to cryptographic authentication while referring to the use of a FIDO authenticator as the FIDO solution, or the authenticator storage solution, glossing over the fact that the private key may be exported under encryption rather than physically kept in the authenticator.

The browser storage solution can easily overcome the two obstacles that FIDO faces in the consumer space. To demonstrate this I have published on GitHub two demo web apps that implement passwordless, phishing-resistant cryptographic authentication with a key pair credential, without relying on an authenticator. In both of them the key pair is generated in the browser by the JavaScript frontend of the app, and kept in the localStorage facility provided by the Web Storage API. One of them uses a “nosql” (MongoDB) backend database to register the public key and store the user data, while the other uses an “sql” database for that purpose.

Pomcor Releases PJCL 1.0.0 on GitHub and npm and Deprecates the Beta Versions of the Pomcor JavaScript Cryptographic Library

In 2018 we published a series of beta versions of the Pomcor JavaScript Cryptographic Library (PJCL), which we called 0.9.0, 0.9.0r1, 0.9.1, 0.9.1r1 and 0.9.1r2. (We shall use semantic versioning to name future versions.) We then had to put the PJCL work on hold, but have now been able to resume development. We have refactored the library as an ES6 module and released version 1.0.0 on GitHub at https://github.com/fcorella/pjcl.git, and on npm.

While testing the refactored version 1.0.0 we found two bugs that we tracked back to version 0.9.1r2. Specifically, we found a bug in function pjclPBKDF2_SHA256 and a bug in function pjclFFCValidateG_256, which caused the JavaScript interpreter to throw exceptions. We fixed the bugs in a maintenance release 0.9.1r3, but we have now archived and deprecated the beta versions and will no longer be maintaining them.

If you want to stay informed about PJCL in the future, please subscribe to GitHub notifications about the pjcl repository.

Random Bit Generation with Full Entropy and Configurable Prediction Resistance in a Node.js Application

This is the fourth and last post of a series describing a proof-of-concept web app that implements cryptographic authentication using Node.js with a MongoDB back-end. Part 1 described the login process. Part 2 described the registration process. Part 3 described login session maintenance. The proof-of-concept app, called app-mongodb.js, or simply app-mongodb, can be found in a zip file downloadable from the cryptographic authentication page.

In app-mongodb, random bits are used on the server side for generating registration and login challenges to be signed by the browser, and for generating login session IDs. On the client side, they are used for generating key pairs and computing randomized signatures on server challenges.

In quest of full entropy

There are established methods for obtaining random bits to be used in web apps. On the client side, random bits can be obtained from crypto.getRandomValues, which is part of the W3C Web Crypto API. On the server side, /dev/urandom can be used in Linux, MacOS and most flavors of Unix. However, neither of these methods guarantees full entropy.

Login Session Maintenance in Node.js using Express and Handlebars

This is part 3 of a series of posts describing a proof-of-concept web app that implements cryptographic authentication using Node.js with a MongoDB back-end. Part 1 described the login process. Part 2 described the registration process. This Part 3 is concerned with login session maintenance in a broader scope than cryptographic authentication. Part 4, concerned with random bit generation, is now available. The proof-of-concept app, called app-mongodb.js, can be found in a zip file downloadable from the cryptographic authentication page.

Update. The name of the constant securityStrength has been changed to rbgSecurityStrength as noted in the last post of the series and reflected in one of the snippets below.

At first glance it may seem that there is no need for login session maintenance in a web app that implements cryptographic authentication with a key pair. Every HTTP request can be authenticated on its own without linking it to a session, by sending the public key to the back-end and proving possession of the private key, as in the login process described in Part 1. That login process relied on the user supplying the username in order to locate the user record, but this is not essential, since the user record could be located in the database by searching for the public key, which is unique with overwhelming probability.

But login sessions provide important login/logout functionality, allowing the user to choose whether to authenticate or not. A member of a site accessible to both members and non-members, for example, may choose to visit the site without authenticating in order to see what information is made available by the site to non-members. Also, the proof of possession of the private key has a latency cost for the user due to the need to retrieve the challenge from the server, and a computational cost for the server and the browser. These costs are insignificant if incurred once per session, but may not be insignificant if incurred for every HTTP request.

The app discussed in this series, app-mongodb.js, implements login sessions in the traditional way using session cookies. Having said that I could stop here. But the Express framework used in the app provides interesting ways of implementing traditional login sessions, which are worth discussing.

Credential Registration for Cryptographic Authentication with Node.js and MongoDB

This is part 2 of a series of posts describing a proof-of-concept web app that implements cryptographic authentication using Node.js, Express, Handlebars, MongoDB and Mongoose. All parts are now available. Part 1 describes the login process. This Part 2 describes the registration process. Part 3 describes login session maintenance. Part 4 is concerned with random bit generation.

Update. The name of the constant securityStrength has been changed to rbgSecurityStrength as noted in the last post of the series and reflected in the snippets below.

Part 1 of this series described the login process of a proof-of-concept Node.js application that implements cryptographic authentication using a MongoDB database back-end. The app, called app-mongodb.js, can be found in a zip file downloadable from the cryptographic authentication page, where it is bundled together with a simpler app that has the same functionality and the same front-end but emulates the database using JavaScript objects, provided for comparison.

This post describes the registration process of app-mongodb.js. The app has a registration page reachable from a link found under a top-of-page login form in the public pages of the app. The registration page has a form where the user enters a username, a first name and a last name, but no password. The first and last names are representative of any info that the user may be asked to provide in a full-fledged application.

The registration process of app-mongodb.js has a structure similar to that of the login process described in Part 1. The browser sends an HTTP POST request to the /register-username endpoint of the server, conveying the username, first name and last name. The server creates a user record, called a “user document” in MongoDB terminology, and responds with a JavaScript POST redirection. The JavaScript POST redirection consists of downloading a script that generates a key pair, signs a server challenge with the private key, and sends the public key and the signature to the /register-public-key endpoint in a second HTTP POST request. The server cryptographically validates the public key, verifies the signature, and adds the public key to the user document.

The following code snippet shows how the server processes the first HTTP POST request, received at the /register-username endpoint.

Cryptographic authentication with Node.js and MongoDB

This is part 1 of a series of posts describing a proof-of-concept web app that implements cryptographic authentication using Node.js, Express, Handlebars, MongoDB and Mongoose. All parts are now available. Part 2 describes the registration process. Part 3 describes login session maintenance. Part 4 is concerned with random bit generation.

Update. The name of the constant securityStrength has been changed to rbgSecurityStrength as noted in the last post of the series and reflected the snippets below.

The PJCL library allows full-stack web developers to use the same cryptographic API on a browser front-end and a Node.js back-end, as explained here. At the last IIW we demoed a web app, implemented using Node.js and Express, that featured cryptographic authentication with a DSA key pair, using PJCL both in the browser to sign a challenge and in the Node.js server to verify the signature. Initial implementations of the app were complicated by having to work around a Firefox bug, which we reported and was confirmed. But eventually we found a simple way of bypassing that bug.

The IIW demo app was very simple. It only had a public “home page” and a private “welcome page”, and it emulated the back-end database using JavaScript objects. We are now releasing a more substantial proof of concept of cryptographic authentication that again uses Node.js and Express, but this time uses a MongoDB database, accessed via a Mongoose driver. Besides using an actual rather than emulated database, the new proof-of-concept app includes features such as on-the-fly login and garbage collection of incomplete user registrations. It also shows how to implement random bit generation with full initial entropy and configurable prediction resistance, which I plan to discuss in another blog post of this series.

The new app is available in a new cryptographic authentication page of the Pomcor site. It is bundled together in a zip file with a simpler app that has the same functionality and the same front-end, but emulates the database using JavaScript objects. The two apps, called app-mongodb.js and app-nodb.js, share the same static files and views. Comparing the two apps may help with understanding the code of the more complex app-mongodb.js. The apps may be run in any Node.js server with access to a MongoDB database and a /dev/random device file, as explained in a README file included in the zip archive.

Second Release of PJCL Expands Functionality Following NIST Cryptographic Specifications

Today we have released version 0.9.1 of the Pomcor JavaScript Crytpographic Library (PJCL). The initial public release provided digital signature functionality, which we had been using internally for our own research on authentication and identity proofing. This release adds key agreement and key derivation functionality. The next release will provide symmetric and asymmetric encryption primitives, including AES and RSA. To be notified of future releases you may ~~sign up for the user forum~~, subscribe to the feed of this blog, or follow me on Twitter (@fcorella). (Update: The PJCL user forum has been discontinued as of May 27, 2018.)

PJCL can be used in any JavaScript environment, both client-side (e.g. in a browser) and server-side (e.g. under Node.js). It comes with extensive documentation on the functionality that it provides, which includes:

Pomcor Releases JavaScript Cryptographic and Big Integer Library

We have just released a beta version of a JavaScript cryptographic library usable in any JavaScript environment and based on very fast big integer arithmetic functionality that may be of interest in its own right.

The Pomcor JavaScript Cryptographic Library (PJCL) is available free of charge for any kind of use, but not under a traditional open source license. The traditional open source paradigm encourages contributions by the developer community at large, but we believe that this paradigm is not well suited to cryptography. To protect the integrity of the cryptographic code, the license prohibits modification of the cryptographic functions.

We have been using the library internally for our own research on authentication and identity proofing, and this first release includes symmetric and asymmetric digital signature functionality, including HMAC, DSA, and ECDSA with NIST curves. Future releases will provide broader cryptographic functionality, including encryption and key exchange. We believe that the library provides the only available JavaScript implementation of DSA, which is important to those wary of the opportunities for hiding backdoors that might be provided by elliptic curve technology.

The underlying big integer functionality includes Karatsuba multiplication. Continue reading “Pomcor Releases JavaScript Cryptographic and Big Integer Library”