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Threshold Niederreiter: chosen-ciphertext security and improved distributed decoding
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DOI：10.1007/s10623-025-01795-6.png)
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Abstract
En 中文
Threshold public-key encryption securely distributes private key shares among multiple participants, requiring a minimum number of them to decrypt messages. We introduce a quantum-resistant threshold public-key encryption scheme based on the code-based Niederreiter cryptosystem that achieves security against chosen ciphertext attacks. A previous attempt was made recently by Takahashi, Hashimoto, and Ogata but we show that it contains a critical security flaw that allow adversaries to exploit malformed ciphertexts to gain information about the secret key. We formalize a generic conversion enhancing security of (classical) public-key encryption from one-wayness against passive attacks to indistinguishability against chosen-ciphertext attacks. The conversion uses a non-interactive zero-knowledge argument with strong security properties to ensure ciphertext well-formedness. We then provide an instantiation for Niederreiter ciphertexts based on recent techniques introduced in the MPC-in-the-head paradigm. The publicly verifiable validity of ciphertexts makes this scheme suitable for threshold public-key encryption and prevents an attack similar to the one on Takahashi-Hashimoto-Ogata scheme. Finally, we introduce a field-switching technique that allows to improve the multi-party computation protocol for decryption, reducing the shared secret key size and computational overhead.
Keywords:
Threshold cryptography
McEliece
Multiparty computation
MPC-in-the-head
Naor-Yung transformation
Journal
D
IF:
1.2
Papers:
124
Citations:
3.2K