RubenSomsen

Segregated Message Signature Scheme (SMSS)

This write-up formalizes a modest adaptation to the regular Schnorr and ECDSA signature scheme, using existing techniques, that allows for signature verification without requiring the message.

The regular signature scheme enables two functions:

1. Proving knowledge of a secret key
2. Tying that proof to a message

Signature verification requires:

• The public key

RubenSomsen

Liquid P2P Loans

This is a variation of the Hodl Hodl contract design for Liquid, but without an arbitrator (not counting Liquid itself). It's pretty simple and similar ideas exist, but it seemed interesting enough to write up and spur some conversation.

I'll begin by explaining the high level concept. For the full details, please examine the steps in the diagram below.

Concept

A contract where the Borrower puts up 1.5x collateral (e.g. 1.5 L-BTC) in order to borrow another asset (e.g. $10k USDT, if we assume that's the price of 1 L-BTC). The borrower can reclaim the collateral if they pay back the loan before expiry. If expiry is reached, the collateral goes to the Lender.

Use cases

• Spending L-BTC without necessarily selling, which

RubenSomsen

Trustless Address Server

Outsourcing handing out addresses to prevent address reuse

Also discussed on bitcoin-dev.

Introduction

Address reuse prevention generally requires interacting with the recipient in order to receive a fresh address for each payment. There are various protocols that ensure no interaction is required such as BIP47[^1] and Silent Payments[^2], though neither is without downsides.

One area that is seemingly underexplored is that of outsourced interaction. BTCPay Server[^3] is an example of this. The sender interacts with a server, which acts on behalf of the recipient and hands out an address from an xpub. The recipient controls and therefore trusts the server, so malicious addresses won't be given out.

RubenSomsen

BIP47 Prague Discussion

This discussion took place at Pizza Day Prague 2022 after a brief discussion on Silent Payments. The main points have been summarized below.

The discussion was mainly between Alekos Filini, Martin Habovštiak, and Ruben Somsen, as well as Daniela Brozzoni, Eric Sirion, Pavol Rusnak, Salvatore Ingala, and others.

This was also posted to the the bitcoin-dev mailing list.

Improving BIP47

RubenSomsen

Spacedollars: Trustless Dollars on a Spacechain

Idea proposed here by Fernando Nieto.

Assuming there is a trustless BTC/USD price oracle, we can burn BTC to create a dollar equivalent amount of "space dollars".

E.g. If the BTC price is $20k, burning 1 BTC gets you 20k space dollars.

The resulting token is the equivalent of the USD: a stable unit of account, but a poor store of value.

RubenSomsen

Blind Merged Mining with covenants ( sighash_anyprevout / op_ctv )

Update: the content of this gist is also explained in this Spacechains video.

This write-up was also published on bitcoin-dev.

Blind Merged Mining (BMM) is the idea of committing the hash of another blockchain into a unique location on the Bitcoin blockchain, and paying a Bitcoin fee to miners for the privilege of deciding this hash and capturing the fees inside the other blockchain. Since miners don’t have to know what the hash represents and are simply incentivized to choose the highest bidder, it requires no extra validation on their part (“blind”). This idea was originally conceived of by Paul Sztorc, but required a specific soft fork. [0]

In essence, BMM is a mechanism that allows external blockchains (altcoins, tokens) to outsource their mining to the Bitcoin blockchain. Instead of burning electricity with ASICs, th

RubenSomsen

SAS: Succinct Atomic Swap

Works today with [single signer ECDSA adaptor signatures][0], or with Schnorr + MuSig.
Other than the explanation below, there's also a diagram and a video.

 
Advantages:

• Requires merely two on-chain transactions for successful completion, as opposed to four
• Scriptless, and one of the chains doesn't need to support timelocks
• Can be used for efficient privacy swaps, e.g. [Payswap][1]

RubenSomsen

Blind Diffie-Hellman Key Exchange (blind ecash)

The goal of this protocol is for Bob to get Alice to perform a Diffie-Hellman key exchange blindly, such that when the unblinded value is returned, Alice recognizes it as her own, but can’t distinguish it from others (i.e. similar to a blind signature).

Alice:
A = a*G
return A

Bob:
Y = hash_to_curve(secret_message)
r = random blinding factor

RubenSomsen

RubenSomsen

Introduction

I'm Ruben Somsen, Bitcoin Sorcerer. I do protocol design in order to enhance Bitcoin.

I'm sponsored by Spiral, Superlunar/Gemini, HRF, and am currently working on Silent Payments with Josie, assisting Davidson with the implementation of Proof-of-Work fraud proofs into Floresta, and Raj with continuing the work on Teleport (Belcher's Coinswap protocol).

I also help maintain the bitcoin-dev mailing list, co-hosted the Unhashed Podcast, founded the Seoul Bitcoin Meetup in 2014, actively co-organizing BitDevs Amsterdam, and on the layer two funding sub-committee of OpenSats.

You can find me on [Twitter](https://twitter.com/SomsenRube