Reusable ‘Payment Codes’ for Privacy: Coming to a Wallet Near You?

Reusable ‘Payment Codes’ for Privacy: Coming to a Wallet Near You?

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Bitcoin Improvement Proposal 47 — or BIP47 — allows wallets to offer “payment codes,” which act as stealth addresses masking the real Bitcoin address where various payments eventually land. Its protocol and specification have been written by developer and early Bitcoin adopter Justus Ranvier, who spoke with us about the wallets currently seeking to be BIP47-compliant.

Also read: Behind Bitcoin’s Big Mac Index: Radoslav Albrecht on Cryptofinance

Justus’s spec notes that payment codes automatically provide for transaction refundability, are SPV-friendly, and positively identify senders to recipients for relational certainty.


Bitcoin.com (BC): Which wallets are looking at implementing BIP47? Which already have, if any?

Justus Ranvier (JR): Samourai Wallet was the first wallet I worked with, and they are very close to launching with payment codes integrated.

justus ranvier bitcoin developerTwo other wallets have expressed tentative interest, but haven’t actively started working on an implementation yet.

I’m currently working with one wallet developer to define a multisig version of extend BIP47.

“The first version of BIP47 did not support multisig because it wasn’t immediately evident that it would be possible, but we’ve recently discovered a way to make it work with reasonable trade-offs compared to the non-multisig version.”

BC: Is this the first such BIP for Bitcoin?

JR: The Stealth Addresses in Darkwallet were the first use of Elliptic Curve Diffie-Hellman (ECDH) addresses in Bitcoin.

Payment codes are designed to address some of the shortcomings of stealth addresses, which may have been responsible for their lack of adoption.

BC: Why would a user opt for Bitcoin with BIP47 rather than a currency which offers native privacy like Dash or Monero?

JR: The “native privacy” advertised by some currencies may turn out to be more marketing hype than reality. We won’t really know until there’s been comprehensive testing of all the different currencies from a privacy perspective.

In the long term, users will prefer the currencies which represent the best investment because they have the best monetary properties.

“If [A privacy-centric] altcoin has inferior monetary properties and Bitcoin can get reasonably close to it in terms of practical privacy, I don’t see how such an altcoin can compete in the long term.”

BC: What primary use cases do you envision for BIP47?

JR: Bitcoin users can use payment codes the way they’ve always wanted to use Bitcoin addresses, without harmful security and privacy side effects.

“You can treat a payment code like your email address – something that changes infrequently (if at all) and that you print on your business card.”

When you receive bitcoins to your payment code, you see the payment code of the sender and can send bitcoins back to them as easily as replying to an email.

Because they are a more natural fit for the way users want to interact with their wallets, I expect that payment codes will replace addresses as the primary way in which Bitcoin users pay each other.

BC: What other coding projects are you working on right now?

JR: I accidentally became a core developer of Open Transactions because there was nobody else available to do it.

Open Transaction presentation by Justus Ranvier
Open Transaction presentation by Justus Ranvier

It’s too soon to talk about details, but we plan on breaking new ground in terms of how Ricardian Contracts can enhance, rather than replace on-chain Bitcoin transactions.

BC: Tell us a bit about your involvement with the Open Bitcoin Privacy Project. What’s up with OBPP these days?

JR: Right now we’re working on finishing up the second round of wallet privacy ratings, which should be released before the end of the year.

We also have a project to measure and graph address reuse in the blockchain and additional privacy recommendations to wallet developers in the pipeline.

Open-Bitcoin-Privacy-Project-Wallet-Privacy-report

BC: Where do you see the crypto-economy in five years?

JR: In five years, I don’t think we’ll talk about the “crypto-economy” anymore. Instead, we’ll talk about the economy and occasionally talk about the “legacy economy.”

“In five years, I think freelancing for Bitcoin will be as common as having a blog is today.”

In five years, there will also be a highly developed darknet drug and contraband economy where many of the sites are operated by rogue law enforcement officers who decided that running a clandestine drug empire was a safer bet than depending on insolvent public sector pension funds.


Justus can be followed on Twitter.

Would you switch wallets if your current provider did not integrate BIP47? Why or why not? Share below!


Featured image courtesy of Dann Online

  • Roger Ver

    This is the kind of positive news coverage that keeps me excited about bitcoin. Great work Amanda!

    • AmandaBJohnson

      Thanks! Justus is a star, I was so glad to nab an interview with him about the great stuff he produces.