BRIDGE · Connecting Symmetric and Asymmetric Cryptography for Leakage and Faults

Symmetric & asymmetric cryptography offer the basic functionalities needed to communicate securely over a channel. Due to their different features and the different algebraic structures they exploit, the interaction between the design of these primitives and the security of their implementation against side-channel & fault attacks so far followed somewhat separated paths. Based on the observation that (i) many emerging challenges for the implementation security of symmetric & asymmetric primitives share similarities and would highly benefit from a more connected approach, and (ii) this is especially true when considering post-quantum asymmetric encryption schemes that include symmetric components and for which current designs are extremely challenging to protect against side-channel & faults attacks, the BRIDGE project aims to develop a unified treatment of symmetric & asymmetric cryptography by leveraging three innovative movements. First, we aim to export the concept of levelled implementation (where different parts of a primitive are protected with countermeasures of varying cost) from symmetric cryptography towards new post-quantum asymmetric schemes that inherently take implementation security as a design criteria. Second, we aim to export the use of larger (possibly prime) fields and more complex algebraic structures used in asymmetric cryptography to deliver advanced functionalities towards new symmetric schemes that guarantee security against side-channel & fault attacks in low-noise contexts that raise fundamental challenges for existing countermeasures. Third, we aim to exploit hard physical learning problems as radically new building blocks applicable to both types of primitives. By combining these movements, we aim to identify disruptive approaches to build new cryptographic schemes offering a better integration between symmetric & asymmetric designs and improvements of their implementation security by orders of magnitude.