Will You Cross the Threshold for Me?

Prasanna Ravi, Martianus Frederic Ezerman, Shivam Bhasin, Anupam Chattopadhyay, Sujoy Sinha Roy
<span title="2021-11-19">2021</span> <i title="Universitatsbibliothek der Ruhr-Universitat Bochum"> <a target="_blank" rel="noopener" href="https://fatcat.wiki/container/yz7ssmvstjhsxiwixprnmyijnq" style="color: black;">Transactions on Cryptographic Hardware and Embedded Systems</a> </i> &nbsp;
In this work, we propose generic and novel side-channel assisted chosenciphertext attacks on NTRU-based key encapsulation mechanisms (KEMs). These KEMs are IND-CCA secure, that is, they are secure in the chosen-ciphertext model. Our attacks involve the construction of malformed ciphertexts. When decapsulated by the target device, these ciphertexts ensure that a targeted intermediate variable becomes very closely related to the secret key. An attacker, who can obtain information about the
more &raquo; ... dependent variable through side-channels, can subsequently recover the full secret key. We propose several novel CCAs which can be carried through by using side-channel leakage from the decapsulation procedure. The attacks instantiate three different types of oracles, namely a plaintext-checking oracle, a decryptionfailure oracle, and a full-decryption oracle, and are applicable to two NTRU-based schemes, which are NTRU and NTRU Prime. The two schemes are candidates in the ongoing NIST standardization process for post-quantum cryptography. We perform experimental validation of the attacks on optimized and unprotected implementations of NTRU-based schemes, taken from the open-source pqm4 library, using the EM-based side-channel on the 32-bit ARM Cortex-M4 microcontroller. All of our proposed attacks are capable of recovering the full secret key in only a few thousand chosen ciphertext queries on all parameter sets of NTRU and NTRU Prime. Our attacks, therefore, stress on the need for concrete side-channel protection strategies for NTRUbased KEMs.
<span class="external-identifiers"> <a target="_blank" rel="external noopener noreferrer" href="https://doi.org/10.46586/tches.v2022.i1.722-761">doi:10.46586/tches.v2022.i1.722-761</a> <a target="_blank" rel="external noopener" href="https://fatcat.wiki/release/7gx3tbfndrcozd33rq36k3b4gy">fatcat:7gx3tbfndrcozd33rq36k3b4gy</a> </span>
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