Falcon Post-Quantum Signature Scheme Proposal

The email delves into the challenges associated with increasing transaction sizes on the blockchain, particularly in the context of post-quantum (PQ) cryptographic schemes. The sender acknowledges an awareness of current efforts to address these issues by selecting the most plausible scheme that, despite efforts, still results in a significant increase in size—20 times larger than current standards. This acknowledgment sets the stage for a deeper inquiry into alternative solutions.

One such solution explored is the concept of batched signing, as opposed to batched verification, within various PQ schemes. The idea is to evaluate this approach for its potential to manage transactions more efficiently in a future where keys and signatures are expected to be much larger. The inquiry suggests that a collective signing mechanism could not only alleviate some of the scalability concerns but also inadvertently promote better fungibility through economic incentives. Specifically, the sender speculates that such a mechanism could make techniques like coinjoin more appealing for the base layer of transactions, thereby enhancing privacy. Although it's noted that privacy improvements are likely to be more pronounced in higher layers of the transaction process.

However, an initial search into one of the PQ schemes, Falcon, indicates that it may not support batched signing. This point underscores the need for further investigation into the capabilities and limitations of various PQ cryptographic schemes in supporting batched transactions. The sender's message, by raising these points, invites further discussion and exploration of how to address the burgeoning issue of transaction scalability and privacy in the era of quantum computing, without compromising on the efficiency or security of blockchain technology.