Present-day cryptography crucially relies on secret-key cryptography, the setting where communicating parties use a shared secret key, hidden to the attacker, to securely encrypt and/or authenticate data. Secret-key cryptography is based on standardized efficient algorithms known as cryptographic primitives, such as block ciphers and hash functions. These act as building blocks for so-called modes of operations, cryptographic algorithms achieving strong security goals for encryption and authentication, and which are orders of magnitude faster than public-key ones.
This project addresses the two shortcomings of current symmetric key cryptography, namely the lack of provable security for existing block ciphers and the lack of flexibility due to fixed parameters in existing implementations of primitives. The project develops new provably secure ciphers with strong security guarantees under the assumption that an attacker only has black box access to a simple underlying component. The investigator explores a new formal model that captures tradeoffs between local computation and key-dependent access in cryptographic attacks, and develops new modes of operation with improved security under this new viewpoint. The project will have broad impact on society by laying the foundations for the development of secret key cryptography which is used to secure modern communications and commerce.
