Coda signature app for Ledger Blue & Ledger Nano S/X

Big disclaimer : This is a work in progress. Don't use it on a Ledger device that is handling or has ever handled private keys associated with any accounts of value.

Run make to check the build, and make load to build and load the application onto the device. Errors try to be helpful and the most common reason for failure is the device being locked, so if something isn't working, that could be the reason. make delete deletes the app.

See Ledger's documentation for further information.

Generally you won't have to run these commands yourself as the codaledgercli library will be installed, but without installing the library, to get the app version, you run:

python3 codaledgercli/__main__.py --request='version'

To generate and return the public key generated with HDindex 11:

python3 codaledgercli/__main__.py --request=publickey --HDindex=11

All of the information for a transaction is contained in two field elements. These are produced by the Coda client. To sign a transaction, the command is then:

python3 codaledgercli/__main__.py --request=transaction --HDindex=1234 --msgx=recipientpkx --msgm=allotherinfo

Developing

codaledgercli

codaledgercli contains the python code that acts as a bridge between the computer and the Ledger device. This means it's also used so that the Coda client and Ledger app can interact. The code in codaledgercli is distributed as a library (this happens by running some commands with setup.py), and it is needed to:

• load and delete the Ledger app on the Ledger device (in the future, the app should be listed on Ledger Live and so that can be used to distribute, load, delete, and interact with the Ledger app).
• interact with the Ledger app. The current functionality consists of sending commands to the Ledger app to:
  • get the app version (taking no additional parameters),
  • generate a keypair from an HDindex (an integer), which results in the public key being sent back to the computer,
  • generate a signature from a message to be signed, and an HDindex with which to generate the keypair used for signing. The python code just acts as a bridge, and the actual Ledger app code is written in C, and found in src.

test

test contains python scripts useful when testing new functionality on the Ledger device. In includes python implementations of elliptic curve arithmetic, poseidon, and signing, so you can make sure hashing is consistent on and off-device, and that signatures generating on device verify as expected.

src

src contains the code that is loaded onto the Ledger device. The loading itself makes use of the python contained the ledgerblue library. This code is loaded using Makefile and depends on the Ledger dev SDK. Instructions on how to load this code onto your Ledger device are here. The comments in files inside src explain more thoroughly what they do, but in brief, it contains all of the code for the app to function, including elliptic curve cryptography, the poseidon hash function, and signature generation. The files in glyphs are used by the code in src, as is nanos_app_coda.gif.

Most of the code in src that relates to the app functioning (for example scrolling, user confirmations, etc) has been influenced heavily by Sia's Ledger app. Extending the app to confirm specific fees, amounts, and recipient pk on the screen of the Ledger device will probably look something like this.