CAKE: Code-Based Algorithm for Key Encapsulation

• Published in: Cryptography and Coding Vol. 10655; pp. 207 - 226
• Main Authors: Barreto, Paulo S. L. M., Gueron, Shay, Güneysu, Tim, Misoczki, Rafael, Persichetti, Edoardo, Sendrier, Nicolas, Tillich, Jean-Pierre
• Format: Book Chapter
• Language: English
• Published: Switzerland Springer International Publishing AG 2017; Springer International Publishing
• Series: Lecture Notes in Computer Science
• Subjects: Code-based cryptography; Key exchange; Post-quantum cryptography
• ISBN: 3319710443; 9783319710440
• ISSN: 0302-9743; 1611-3349; 1611-3349
• DOI: 10.1007/978-3-319-71045-7_11

Current widely-used key exchange (KE) mechanisms will be vulnerable to quantum attacks when sufficiently strong quantum computers become available. Therefore, devising quantum-resistant replacements that combine efficiency with solid security guarantees is an important and challenging task. This paper proposes several contributions towards this goal. First, we introduce “CAKE”, a key encapsulation algorithm based on the QC-MDPC McEliece encryption scheme, with two major improvements: (a) the use of ephemeral keys that defeats a recent reaction attack against MDPC decoding of the corresponding encryption scheme and (b) a highly efficient key generation procedure for QC-MDPC-based cryptosystems. Then, we present an authenticated key exchange protocol based on CAKE, which is suitable for the Internet Key Exchange (IKE) standard. We prove that CAKE is IND-CPA secure, that the protocol is SK-Secure, and suggest practical parameters. Compared to other post-quantum schemes, we believe that CAKE is a promising candidate for post-quantum key exchange standardization.