Universal Coding for Shannon Ciphers under Side-Channel Attacks
Yasutada Oohama, Bagus Santoso
TL;DR
This paper advances universal coding for Shannon ciphers under side-channel attacks by proving the existence of encoder/decoder families that achieve reliable decoding for legitimate users while guaranteeing vanishing information leakage for any plaintext distribution and fixed side-channel model. The authors introduce a perfect universality result: for any pair of rates (R_A,R) and any source and channel distributions p_X, p_{KZ}, there exist codes with decoding error decaying exponentially and leakage decaying at a computable exponent G(R_A,R|p_{KZ}). The approach blends information spectrum methods with type-based analysis and introduces a new leakage-bound tool (Upsilon) and a meta-converse lemma, yielding a constructive, distribution-independent coding scheme. These results strengthen the practical relevance of secure source coding under side-channel leakage by guaranteeing robust performance across a wide class of devices and plaintext statistics.
Abstract
We study the universal coding under side-channel attacks posed and investigated by Oohama and Santoso (2022). They proposed a theoretical security model for Shannon cipher system under side-channel attacks, where the adversary is not only allowed to collect ciphertexts by eavesdropping the public communication channel, but is also allowed to collect the physical information leaked by the devices where the cipher system is implemented on such as running time, power consumption, electromagnetic radiation, etc. For any distributions of the plain text, any noisy channels through which the adversary observe the corrupted version of the key, and any measurement device used for collecting the physical information, we can derive an achievable rate region for reliability and security such that if we compress the ciphertext with rate within the achievable rate region, then: (1) anyone with secret key will be able to decrypt and decode the ciphertext correctly, but (2) any adversary who obtains the ciphertext and also the side physical information will not be able to obtain any information about the hidden source as long as the leaked physical information is encoded with a rate within the rate region.
