Cryptology ePrint Archive: Report 2020/403

Bringing Order to Chaos: The Case of Collision-Resistant Chameleon-Hashes

David Derler and Kai Samelin and Daniel Slamanig

Abstract: Chameleon-hash functions, introduced by Krawczyk and Rabin at NDSS 2000, are trapdoor collision-resistant hash-functions parametrized by a public key. If the corresponding secret key is known, arbitrary collisions for the hash function can be efficiently found. Chameleon-hash functions have prominent applications in the design of cryptographic primitives, such as lifting non-adaptively secure signatures to adaptively secure ones. Recently, this primitive also received a lot of attention as a building block in more complex cryptographic applications ranging from editable blockchains to advanced signature and encryption schemes.

We observe that in latter applications various different notions of collision-resistance are used, and it is not always clear if the respective notion does really cover what seems intuitively required by the application. Therefore, we revisit existing collision-resistance notions in the literature, study their relations, and - using the example of the recent redactable blockchain proposals - discuss which practical impact different notions of collision-resistance might have. Moreover, we provide a stronger, and arguably more desirable, notion of collision-resistance than what is known from the literature. Finally, we present a surprisingly simple and efficient black-box construction of chameleon-hash functions achieving this strong notion.

Category / Keywords: public-key cryptography / Chameleon-hash

Original Publication (with minor differences): IACR-PKC-2020

Date: received 9 Apr 2020

Contact author: david at dfinity org, kaispapers@gmail com, daniel slamanig@ait ac at

Available format(s): PDF | BibTeX Citation

Version: 20200413:102727 (All versions of this report)

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