Bitcoin researchers are focusing on using "hash-based signatures" for quantum-resistant upgrades.

PANews reported on December 12th, citing DL News, that in a revised paper published on December 5th, Blockstream researchers Mikhail Kudinov and Jonas Nick explored several methods to upgrade the Bitcoin blockchain to make it quantum resistant. They argue that hash-based signatures are a highly attractive post-quantum solution because their security relies solely on the assumption of a hash function similar to Bitcoin's fundamental design. In an email to the Bitcoin developer mailing list introducing their research, Kudinov stated, "These schemes underwent extensive cryptanalysis during the post-quantum standardization process at the National Institute of Standards and Technology (NIST), which increases confidence in their robustness."

Hash-based signatures rely on hash functions, mathematical algorithms considered quantum-resistant because, unlike the public-key cryptography used in Bitcoin, hash functions are difficult for quantum algorithms to break. Hash functions can be secured by simply increasing their output size to handle the potential brute-force searches by quantum computers, thus expanding the search space and ensuring the security of applications like digital signatures. However, how developers will implement hash-based signatures is still under discussion. Decisions need to be made regarding issues such as keeping verification costs low, standardizing various hash-based signature implementations, and whether the entire network's history is needed to verify transactions.