Welcome,
Project Eleven is an applied quantum computing and cryptography group.
Announcements incoming from us this week. Stay tuned on X and LinkedIn.
Bitcoin’s place as the 800 pound gorilla amongst cryptocurrencies is well earned. Enormous warehouses of ASICs secure its blockchain, robust cryptography protects BTC holders and transactions, and its ideological pull has turned out to be far more potent than any would-be challenger currency.
Bitcoin has neither security guards or bank vaults; it is secured by cryptography and hash power, and up to now, these have served Bitcoin well. As large-scale, fault-tolerant quantum computers come online, this will change. As soon as Shor’s algorithm can break a 256-bit key, a fundamental assumption will be invalidated: Elliptic curve cryptography will no longer be reliable security for Bitcoin. If Bitcoin is not quantum-secure by then, what happens next is anyone’s guess: Mass exodus and collapse of the currency? Neutral or ignorant responses? An immediate emergency effort to upgrade the protocol?
In the next few years then, Bitcoin will have to make some hard choices. Upgrading to post-quantum cryptography presents at least three major issues.
- Which post-quantum signature should replace ECDSA?
- Given that post-quantum signature sizes are 10 - 100x the size of ECDSA signatures, does Bitcoin’s transaction throughput fall 10 - 100x, or does the block size change?
- 3.3M BTC ($300B) has not moved in over 10 years. If owners cannot or do not move these coins to post-quantum signatures, what happens to them? Are they declared invalid and effectively destroyed, allowed to remain vulnerable and potentially stolen, or preserved through some other mechanism?
Each of these questions deserves its own discussion, but the latter two will be most difficult to resolve. While the first question - choosing a suitable quantum-resistant signature scheme - is technically complex, it is not an ideologically fraught question. It’s a question of straightforward tradeoffs in terms of security, speed, ease of implementation and signature size.
The questions around block size and preserving dormant BTC will spark much more debate within the community. Much time, energy and emotions have already been spent on block size, as in the block size debate of 2015 - 2017, which resulted in multiple Bitcoin forks.
For context, increasing block size has a centralizing effect on the network, in that larger blocks mean BTC nodes require bigger, more expensive servers. Conversely, implementing post-quantum signatures without increasing block size will reduce the amount of transactions the network can handle and make it far more expensive to transact - the same pool of Bitcoin holders will be bidding for 10 - 100x fewer transaction slots. This is a centralizing effect too, in that larger entities can better afford to transact.
Deciding the fate of dormant BTC also touches on core Bitcoin principles. This is a community and movement born out of libertarian and techno-anarchist leanings, who want control and sovereignty over their property, and expect that nobody should be able to interfere with their crypto. Burning coins that have not been updated to post-quantum signatures is an unprecedented violation of this tenet. On the other hand, leaving coins vulnerable allows a quantum computer owner to steal those Bitcoin, also a violation of property rights, and a potentially threat to the network’s overall security if enough BTC are stolen by quantum computers.
Solving these problems will require hard thinking, debate and campaigning. Ultimately, Bitcoiners will have to weigh their commitments to decentralization, immutability, usability, and security, and decide which values they’re willing to compromise in order to ensure Bitcoin thrives post-QDay.
We’re currently working on a quantum cryptanalysis project. You can get in touch with us via [email protected] if you’d like to learn more, or are working in the area.
Until next time,
The Project Eleven Team
- Cloudflare’s intro to Lattices
- Jameson Lopp on quantum-vulnerable BTC
- Scott Aaronson on certified quantum randomness
- Certified quantum randomness using a trapped-ion quantum processor
- Block size wars
- Vitalik on the block size wars
Update your email preferences or unsubscribe here
© 2025 Project Eleven
54 W 21st St
New York, New York 10010, United States of America