Welcome to the resource topic for 2025/1193
Title:
Non-Homomorphic Key Blinding from Symmetric Primitives
Authors: Thomas Bellebaum
Abstract:Key Blinding Signature Schemes allow to derive so-called
blinded keys from public keys, which can be used to verify signatures
created with the secret key. At the same time, neither the blinded keys
nor their signatures disclose from which public key they were derived,
effectively implementing pseudonyms for one’s identity.
In search of conservative schemes, we deviate from the homomorphism-
based re-randomization approach in favor of a novel proof of knowledge-
based approach. To authenticate a message, a signer proves that they
know an original keypair and a valid way to commit to the corresponding
verification key to derive a given blinded key. We provide a framework
for such constructions and indicate how MPC-friendly block ciphers and
one-way functions may be used for efficient instantiations. While the
general framework’s security arguments are stated in the random oracle
model, we show a natural instantiation approach whose security can be
based on collision-resistance and pseudorandomness instead. The result
is the first standard model construction of key blinding.
Using our framework, we identify a shortcoming in the usual definition
of unlinkability for key blinding signature schemes, which we rectify by
considering an additional notion called targeted unlinkability.
ePrint: https://eprint.iacr.org/2025/1193
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