Double-authentication-preventing signatures

作者：Poettering Bertram^*; Stebila Douglas

来源：International Journal of Information Security, 2017, 16(1): 1-22.

DOI：10.1007/s10207-015-0307-8

• Digital signatures
• Double signatures
• Dishonest signer
• Coercion
• Compelled certificate creation attack
• Self-enforcement
• Two-to-one trapdoor functions

Digital signatures are often used by trusted authorities to make unique bindings between a subject and a digital object; for example, certificate authorities certify a public key belongs to a domain name, and time-stamping authorities certify that a certain piece of information existed at a certain time. Traditional digital signature schemes however impose no uniqueness conditions, so a trusted authority could make multiple certifications for the same subject but different objects, be it intentionally, by accident, or following a (legal or illegal) coercion. We propose the notion of a double-authentication-preventing signature, in which a value to be signed is split into two parts: a subject and a message. If a signer ever signs two different messages for the same subject, enough information is revealed to allow anyone to compute valid signatures on behalf of the signer. This double-signature forgeability property discourages signers from misbehaving-a form of self-enforcement-and would give binding authorities like CAs some cryptographic arguments to resist legal coercion. We give a generic construction using a new type of trapdoor functions with extractability properties, which we show can be instantiated using the group of sign-agnostic quadratic residues modulo a Blum integer; we show an additional application of these new extractable trapdoor functions to standard digital signatures.

• 出版日期2017-2