In this paper, we provide a modular security analysis of the handshake in TLS version 1.2 and a slightly sanitized version of the handshake in the current draft of TLS version 1.3, following the constructive cryptography approach of Maurer and Renner (ICS 2011). We provide a deconstruction of the handshake into modular sub-protocols and a security proof for each such sub-protocol. We also show how these results can be combined with analyses of the respective record layer protocols, and the overall result is that in all cases the protocol constructs (unilaterally) secure channels between the two parties from insecure channels and a public-key infrastructure. This approach ensures that (1) each sub-protocol is proven in isolation and independently of the other sub-protocols, (2) the overall security statement proven can easily be used in higher-level protocols, and (3) TLS can be used in any composition with other secure protocols.
In more detail, for the key-exchange step of TLS 1.2, we analyze the RSA-based and both Diffie-Hellman-based variants (with static and ephemeral server key share) under a non-randomizability assumption for RSA-PKCS and the Gap Diffie-Hellman assumption, respectively; in all cases we make use of random oracles. For the respective step of TLS 1.3, we prove security under the Decisional Diffie-Hellman assumption in the standard model. In all statements, we require additional standard computational assumptions on other primi- tives. In general, since the design of TLS is not modular, the constructive decomposition is less fine-grained than one might wish to have and than it is for a modular design. This paper therefore also suggests new insights into the intrinsic problems incurred by a non-modular protocol design such as that of TLS.Category / Keywords: cryptographic protocols / TLS Date: received 7 Jan 2014, last revised 22 Apr 2015 Contact author: btackmann at eng ucsd edu Available format(s): PDF | BibTeX Citation Note: Added material for the current draft of TLS 1.3, proving a slightly sanitized version of the suggested new handshake based on DDH. Version: 20150422:144533 (All versions of this report) Short URL: ia.cr/2014/020 Discussion forum: Show discussion | Start new discussion