Subject: [bitcoindev] Hardforking Bitcoin to SLH-DSA (Future Proofing)

From: scott beeker <[email-masked]>
Date: Wed, 16 Oct 2024 17:45:29 -0700 (PDT)

Hardforking Bitcoin to SLH-DSA

Bitcoin's transition to a post-quantum cryptographic algorithm like SLH-DSA 
(Stateless Hash-Based Digital Signature Algorithm) would be a significant 
and complex undertaking. Here's an analysis of the potential process and 
implications:
Motivation for the Transition

The primary reason for considering a transition to SLH-DSA would be to 
protect Bitcoin against potential threats from quantum computers. While 
quantum computers capable of breaking Bitcoin's current elliptic curve 
cryptography are not yet a reality, the cryptocurrency community is 
increasingly aware of the need to prepare for this eventuality.
Technical Aspects of the Transition 
Signature Scheme Replacement

The current Bitcoin protocol uses the Elliptic Curve Digital Signature 
Algorithm (ECDSA) for transaction signatures. Replacing this with SLH-DSA 
would require substantial changes to the core protocol[1].
Key and Signature Sizes

One of the main challenges in implementing SLH-DSA for Bitcoin would be 
dealing with the increased key and signature sizes:

Algorithm
Public Key Size
Signature Size
ECDSA
33 bytes
71-73 bytes
SLH-DSA
32-64 bytes
7,856-49,216 bytes

The significantly larger signature sizes of SLH-DSA would have implications 
for block size, transaction throughput, and network bandwidth 
requirements[1].
Performance Considerations

SLH-DSA is known for its strong security properties but comes with 
performance costs. It has longer signing times compared to ECDSA, which 
could affect transaction processing speeds[1].
Implementation ChallengesConsensus Changes

Implementing SLH-DSA would require a hard fork of the Bitcoin network, as 
it involves fundamental changes to the consensus rules. This would need 
widespread agreement among miners, node operators, and users.
Backward Compatibility

The transition would need to address backward compatibility issues, 
potentially requiring a period where both ECDSA and SLH-DSA signatures are 
supported to allow users time to migrate their funds to new addresses.
Wallet Software Updates

All Bitcoin wallet software would need to be updated to support the new 
signature scheme, including key generation, signing, and verification 
processes.
Potential BenefitsQuantum Resistance

The primary benefit would be Bitcoin's resistance to attacks from quantum 
computers, ensuring the long-term security of the network[1].
Conservative Security Approach

SLH-DSA is considered a conservative choice for post-quantum cryptography, 
as it relies on the well-studied security of hash functions rather than 
newer mathematical problems like lattices[1].
Potential DrawbacksIncreased Resource Requirements

The larger signature sizes would increase the storage and bandwidth 
requirements for running Bitcoin nodes, potentially leading to increased 
centralization.
Transaction Costs

Larger signatures could result in higher transaction fees, as more 
blockchain space would be required for each transaction.
Complexity

The transition process itself would be complex and risky, potentially 
introducing vulnerabilities if not executed correctly.
Conclusion

While transitioning Bitcoin to SLH-DSA is technically possible, it would be 
a monumental undertaking requiring extensive planning, testing, and 
community consensus. The cryptocurrency community would need to carefully 
weigh the long-term security benefits against the short-term disruption and 
increased resource requirements. As quantum computing advances, this topic 
is likely to become increasingly relevant in discussions about Bitcoin's 
future.

Citations:
[1] We wrote the code, and the code won | Trail of Bits Blog 
https://blog.trailofbits.com/2024/08/15/we-wrote-the-code-and-the-code-won/
[2] SLotH -- An SLH-DSA/SPHINCS+ Hash-Based Signature Accelerator 
https://github.com/slh-dsa/sloth
[3] Cryptographic Right Answers: Post Quantum Edition - Latacora 
https://www.latacora.com/blog/2024/07/29/crypto-right-answers-pq/
Is your feature related to a problem, if so please describe it.

https://www.csoonline.com/article/3562701/chinese-researchers-break-rsa-encryption-with-a-quantum-computer.html/amp/

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