CAREER: Exposure-Resilient Cryptography

New York University, New York NY

Investigators

Abstract

Abstract: Exposure-Resilient Cryptography concerns the important problem of key exposure and general information leakage. Exposure of such information poses one of the most serious and common threats to employing cryptography in real life. For example, cryptographic computations (decryption, signature generation, etc.) are often performed on a relatively insecure device (e.g., a mobile device or an Internet-connected host) which cannot be trusted to maintain secrecy of the private key. Thus, the goal of Exposure-Resilient Cryptography is to design solutions that will limit (or even completely eliminate) the negative consequences of such an exposure in various cryptographic scenarios. In particular, this research concentrates on the design of various key evolving schemes and the problem of partial key exposure. The paradigm of secret key evolution over time invloves updating one's secret key such that key leakage at given period(s) compromises the security of other periods to the minimal extent possible. The investigators examine two such models. Forward-secure schemes update secret key locally, and seek to protect the security of all the past periods when the current key is exposed. In contrast, bidirectionally-secure schemes use secure key updates, but protect all non-exposed periods: both in the past and in the future. In either model, the public information (e.g., public keys) are not affected by the secret key evolution. The problem of partial key exposure concerns the scenario where most but not all secret information has been leaked. The main question studied in this setting is how can valuable secret information be stored or represented in such a way that almost complete exposure of its representation still guarantees the secrecy of the actual, embedded secret?