🤖 AI Summary
This work addresses the performance limitations of existing isogeny-based key exchange protocols, which remain viable despite the cryptanalysis of SIDH and its variants via classical polynomial-time key recovery attacks. We present the first adaptation of the high-dimensional isogeny-based POKE public-key encryption scheme into a key encapsulation mechanism suitable for key exchange. A systematic performance evaluation at NIST security level 1 demonstrates that our POKE-based key exchange significantly outperforms current isogeny-based alternatives: it achieves approximately 21.21× speedup over terSIDH and 64.97× over CSIDH. These results establish POKE as a highly promising candidate for post-quantum key exchange, offering both strong security foundations and markedly improved efficiency.
📝 Abstract
In this paper, we present a comparative performance analysis of the POKE-based key exchange and SIDH variants. SIDH gained attention for its small key size and efficient performance, and has been selected as an alternate candidate in NIST PQC Round 4. However, following the key recovery attack by Castryck and Decru in 2022, SIDH was shown to be vulnerable to polynomial-time attacks on classical computers, undermining its security and removing it from consideration. Given that SIDH was regarded as the leading isogeny-based algorithm, several countermeasures, such as MSIDH, MD-SIDH, and bin/terSIDH have been proposed. However, these approaches still face performance limitations. Meanwhile, POKE, proposed by Basso and Maino at Eurocrypt 2025, is an isogeny-based public key encryption scheme that combines a SIDH-like protocol with higher-dimensional isogenies and has drawn attention for its efficient performance. In this work, we adapt POKE into a key exchange algorithm and benchmark it against M-SIDH, terSIDH, and CSIDH. Targeting NIST security level 1, POKE-based KEM is approximately 21.21 times faster than terSIDH and 64.97 times faster than CSIDH, showing that the POKE-based KEM is currently the most promising isogeny-based key exchange candidate.