OpenPGP Secp256k1 Smartcard Wallet

Turn your smartcard (e.g. Yubikey) into a secp256k1 wallet! This repo provides:

• A CLI for generating a keypair on your smartcard and signing messages with it
• An API for signing and exporting the public key from your smartcard device

⚠️ A Word of Caution

Although you can turn an inexpensive smartcard hardware device into a signer, it is inferior to using a true hardware wallet, and should not be a replacement for one. Yubikeys do not have a display, so all data must pass through your (presumably internet-connected) general purpose computer. Although this tool will help you generate a key securely (i.e. on the device, where it cannot be exported), you have no way to verify what you are signing on the secure device, which reduces the system's safety.

This repo was designed for multisig setups where several secondary signers are distributed, but if you are securing a large amount of value, you should ensure your primary signer is using a hardware wallet or secure setup. Be safe! ✌️

Using the CLI

You are likely using a Yubikey; if you are, read all about getting it setup here. You can skip the key setup parts. Once you have the device configured as you'd like, build this repo:

make build

Then generate an secp256k1 keypair on the card:

./bin/wallet generate

This will prompt you for your user PIN and admin PIN.

Once you have a key on the card, you can export its public key:

./bin/wallet pubkey

Similarly, you may pass data to sign, which may be encoded either as a hex or ASCII string:

./bin/wallet sign some_text
./bin/wallet sign 0x1234

Note that by default, the message is a pre-image and the hash type is sha256. However, you may pass a --hash flag to use keccak256 or none. If you use none, your input data must be a 32 byte hex string.

Using the API

Alternatively, you may export the pubkey or sign from the API. Note that the API does not expose the ability to generate a key.

import (
  "github.com/alex-miller-0/openpgp-secp256k1-wallet/pkg/api"
)

// Hash `data` with keccak256 and sign
sig, err := api.Sign(data, userPin, "keccak256")

// Pass pre-hashed data to be signed
// `data` must be 32 bytes in this case!
sig, err = api.SignPrehashed(data, userPin)

// Export the uncompressed pubkey
pubkey, err := api.GetPub(userPin)