Turn your Trezor hardware wallet into a Stellar hardware wallet

TLW

Introduction:
In Bitcoin eco-system and there are many manufacturers providing bitcoin hardware wallet service. Since Ethereum and many other popular cryptocurrencies share the same private key format as bitcoin, wallet such as Ledger and Trezor also support storing of Litecoin, Ether, ERC20 tokens etc.

However, currently these wallet users cannot use their wallet to store lumen and another asset on Stellar Network. This indeed can be realised as Trezor claims to be more than simply a hardware wallet but also a password manager and a login token! https://blog.trezor.io/trezor-security-beyond-bitcoin-c99f27b18b6b

We use trezor to encrypt a urandom(32) bytes and use that to generate a Stellar keypair. With the generated Stellar keypair the user will be able to sign all kinds of transaction.

By using python scripts introduced here, the user is able to turn his or her Trezor into a secure Stellar hardware wallet too.
https://github.com/1Hr1619SxTuTBC3qYZJ1rkfAxrvWnt7bt3/Trezor-Stellar-Integration

Motivation:
Trezor as one of the most successful hardware wallet manufacture has a huge customer base. Supporting Trezor with Stellar assets can be helpful in building Stellar's reputation and user base.

Future development:
1. Completing all the operation types. Currently it enables checking balance, sending lumen, sending assets and trusting assets.
2. Contacting Satoshi Lab to add this project here: http://doc.satoshilabs.com/trezor-apps/index.html
3. Build up a user friendly interface: web+app+desktop.
4. Integrate with current Stellar exchanges, remittance and wallet providers.

Please help testing out the functions, I personally has tried all of them and worked fine for me. Suggestions are very welcome. Thanks.

zcc

I'm happy to see that I'm not the only one working on Trezor integration!

However, it appears that you're only using the encryption functions of the Trezor and not using it for signing transactions. This does provide some additional security, but you're exposing the private key to the user's computer and it could be intercepted by malware running on their machine.

The real strength of the Trezor is that it's able to sign transactions without ever making the private key available so there's no possibility of it being stolen.

I'm not trying to discourage you, but as it is currently this project is not really a Trezor wallet, it's an encrypted wallet that stores the key offline.

Also, it appears that you've committed your Stellar_wallet.json file to github. Hopefully not a big deal since it's encrypted, but I wanted to let you know in case this wasn't intentional.

TLW

zcc Thank you very much for your feedback, are you saying that the signing transaction function must be executed on the wallet and the wallet only pass out transaction XDR?

zcc

TLW Yes, exactly. The program running on the user's machine sends the transaction hash (or the full transaction) to the Trezor. Then, the Trezor sends back the signature without ever making the private seed available.

Sending the full transaction to the Trezor allows the user to confirm what's going to happen, but you may hit memory issues and usability issues since the screen is very small.

For Stellar, you don't need to send back the XDR, just the bytes representing the signature and you can build the XDR for the transaction using the SDK.

@dupe is working on Ledger integration and has made really good progress, you should take a look at his thread: https://galactictalk.org/d/484-ledger-nano-s-hardware-wallet-integration

TLW

zcc In order to do that, I will need to contact Satoshi lab to update their firmware if I understand it correctly. I will definitely keep working on this and report the progress. Thank your valuable input. By the way, I did put up the stellar_wallet.json file up there on purpose just to show how it looks like.

zcc

TLW Their firmware is open source and they provide a tool to flash custom firmware on a Trezor, if you're comfortable working with C.

The approach I'm taking is to first modify their firmware to include a generic ED25519 signing method and then, once I have that figured out, a Stellar-specific method that's aware of XDR so that the user will be able to see exactly what they're signing.

After that, it'll be a matter of convincing them to add it to the official firmware!

Fanbingxia

Hey, this sounds really interesting, we want our website to include Trezor access as well. However, your python code require local access to the device. Any idea on how can this be done remotely from a web server?

TLW

Fanbingxia The process we used here is that the user first randomly generate a key file and then encrypt it with their Trezor. Everytime they need to login into their stellar account, they will need to use their trezor to decrypt account information (private key) stored locally. It is not recommanded to use on a website because you don’t want users to type in their encrypted info every time. The way to solve this would be storing the seed inside trezor but doing so involves updating the firmware of Trezor. We are contacting Trezor developing team to enable stellar transaction. Stay tuned, cheers.

Fanbingxia

TLW Thank you very much for your instruction on how this can potentially work on the website. Here is a demonstration of incorporating Trezor with our web wallet. We have to admit that this is not as secure as hardware wallet for the reason pointed out above but still, it saves people from storing Stellar seed on their own computer. https://www.youtube.com/watch?v=BrCIAZR4PUI