An experimental distributed JWT token cracker built using Node.js and ZeroMQ. It can be used to discover the password (or “secret”) of an unencrypted JWT token using a HS256 signature.

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Through NPM:

npm i -g distributed-jwt-cracker

Requires ZeroMq libraries to be already installed in your machine.



To start a new server:

jwt-cracker-server <jwtToken> [options]

The following options are available:

option description type default
-p, –port The port used to accept incoming connections number 9900
-P, –pubPort The port used to publish signals to all the workers number 9901
-a, –alphabet The alphabet used to generate the passwords string “abcdefghijklmnopqrstuwxyzABCDEFGHIJKLMNOPQRSTUWXYZ0123456789”
-b, –batchSize The number of attempts assigned to every client in a batch number 1000000
-s, –start The index from where to start the search number 0

Example, using the example JWT.io token over a simple alphabet:

jwt-cracker-server eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgQ -a=abcdefghijklmnopqrstuwxyz


To start a new client:

jwt-cracker-client [options]

The following options are available:

option description type default
-h, –host The hostname of the server string “localhost”
-p, –port The port used to connect to the batch server number 9900
-P, –pubPort The port used to subscribe to broadcast signals (e.g. exit) number 9901


jwt-cracker-client --host=localhost --port=9900 --pubPort=9901

The making of

This project has been thoroughly discussed in two articles published on RisingStack community blog:

ZeroMQ & Node.js Tutorial - Cracking JWT Tokens


Everyone is very welcome to contribute to this project. You can contribute just by submitting bugs or suggesting improvements by opening an issue on GitHub.


Licensed under MIT License. © Luciano Mammino.