Merged Bitcoin: Proof of Work Blockchains with Multiple Hash Types

Fuente: arXiv
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Autores principales: Blake, Christopher, Feng, Chen, Wang, Xuachao, Yu, Qianyu
Formato: Preprint
Publicado: 2026
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author Blake, Christopher
Feng, Chen
Wang, Xuachao
Yu, Qianyu
author_facet Blake, Christopher
Feng, Chen
Wang, Xuachao
Yu, Qianyu
contents Proof of work blockchain protocols using multiple hash types are considered. It is proven that the security region of such a protocol cannot be the AND of a 51\% attack on all the hash types. Nevertheless, a protocol called Merged Bitcoin is introduced, which is the Bitcoin protocol where links between blocks can be formed using multiple different hash types. Closed form bounds on its security region in the $Δ$-bounded delay network model are proven, and these bounds are compared to simulation results. This protocol is proven to maximize cost of attack in the linear cost-per-hash model. A difficulty adjustment method is introduced, and it is argued that this can partly remedy asymmetric advantages an adversary may gain in hashing power for some hash types, including from algorithmic advances, quantum attacks like Grover's algorithm, or hardware backdoor attacks.
format Preprint
id arxiv_https___arxiv_org_abs_2601_09090
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Merged Bitcoin: Proof of Work Blockchains with Multiple Hash Types
Blake, Christopher
Feng, Chen
Wang, Xuachao
Yu, Qianyu
Cryptography and Security
Proof of work blockchain protocols using multiple hash types are considered. It is proven that the security region of such a protocol cannot be the AND of a 51\% attack on all the hash types. Nevertheless, a protocol called Merged Bitcoin is introduced, which is the Bitcoin protocol where links between blocks can be formed using multiple different hash types. Closed form bounds on its security region in the $Δ$-bounded delay network model are proven, and these bounds are compared to simulation results. This protocol is proven to maximize cost of attack in the linear cost-per-hash model. A difficulty adjustment method is introduced, and it is argued that this can partly remedy asymmetric advantages an adversary may gain in hashing power for some hash types, including from algorithmic advances, quantum attacks like Grover's algorithm, or hardware backdoor attacks.
title Merged Bitcoin: Proof of Work Blockchains with Multiple Hash Types
topic Cryptography and Security
url https://arxiv.org/abs/2601.09090