Proton mail--a private and secure email provider we use and encourage our clients to use--rolled out a limited access bitcoin wallet for its proton visionary account holders. We expect Proton Wallet to be rolled out to every proton user in the not too distant future. In anticipation of this eventuality, we took a look at the offering, concluding that it provides pretty good security and privacy but should not be relied upon for air-tight anonymity. This is because of certain design decisions and because of bitcoin's own privacy limitations.

Proton Wallet features:

• Open source

• Self-custodial

• Supports auto-changing addresses

• 2 Factor Authentication

• Wallet, transaction metadata, and seed phrases are encrypted using your Proton username and password

• Send BTC to any Proton wallet email address

• Send transactions to many recipients

• Passphrase Support

• Biometric Unlock

• Use Proton Sentinel to further secure your wallet

  • At this time, there is not much information on how Sentinel works with your wallet. We're not sure of the privacy implications just yet.

• Account recovery

  • via Proton account recovery or mnemonic recovery

• Encrypted Notes and Contacts for transactions

In combination, these characteristics give users similar levels of transparency, security, and functionality of some of the better open source bitcoin wallets on the market today which have proven to provide good enough security and privacy for the vast majority of users. You can expect the same strong security from the rest of the Proton ecosystem.

However, the architecture of the wallet leaves some room for strong privacy to be broken:

• Proton servers can see your unused bitcoin addresses

• To send transactions through the wallet, Proton servers must temporarily have the transaction data necessary to broadcast them to the Bitcoin network.

• In the course of sending bitcoin from one Proton Wallet to another Proton Wallet, Proton servers know the sender's email address and the recipients address temporarily but do not store that information.

• Ships with no coin control

• BTC price data is queried from your addresses

  • While Proton servers can see which addresses are queried, they don’t store these queried addresses or any balances on Proton servers.

But the good news is Proton says coin control is the next feature expected to be added and the Proton servers purge addresses once they've been sent to the account holder for use as well as any transaction data after a transaction has been confirmed.

The Proton Wallet team was working on implementing support for coinjoins via whirlpool but with the arrest of the Samourai team, Proton has decided to put this feature on hold. You can learn more about Samourai legal battle or choose to donate directly.

"Users like Alice and Bob who need the most privacy may want to consider using a third-party coinjoin service before and after their transactions to mix their Bitcoin with others and break the link in the blockchain history."

Interested users should keep in mind that Bitcoin, in its current form, has privacy limitations and by using Proton Wallet you're relying on Proton to be honest and purge certain records once they're not needed, either via technical controls or manual record purges. Having said that, Andy Yen recently stated on the Opt Out Podcast that their audits, court cases, and Swiss law prove they are acting and will continue to act in the best interest of their users.

Other features we'd like to see implemented:

• Connect to other bitcoin nodes including your own

• Connect via Tor

• support for BIP 47 (Paynyms)

• support for BIP 352 (Silent Payments)

• Further technical documentation around how data is handled

We'd also love to see Zcash (ZEC) and Monero (XMR) integrated into the Proton Wallet. These crypto-assets offer best in class privacy for users and are the most liquid, commercially integrated private monies available on the market today.

If you're interested in beefing up your own crypto-asset security as well as your online privacy, please reach out and our team will develop a bespoke personal care plan tailored specifically for you.