Tag size does matter: attacks and proofs for the TLS record protocol

  • Authors:
  • Kenneth G. Paterson;Thomas Ristenpart;Thomas Shrimpton

  • Affiliations:
  • Information Security Group, Royal Holloway, University of London, UK;Dept. of Computer Sciences, University of Wisconsin-Madison;Dept. of Computer Science, Portland State University

  • Venue:
  • ASIACRYPT'11 Proceedings of the 17th international conference on The Theory and Application of Cryptology and Information Security
  • Year:
  • 2011

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Abstract

We analyze the security of the TLS Record Protocol, a MAC-then-Encode-then-Encrypt (MEE) scheme whose design targets confidentiality and integrity for application layer communications on the Internet. Our main results are twofold. First, we give a new distinguishing attack against TLS when variable length padding and short (truncated) MACs are used. This combination will arise when standardized TLS 1.2 extensions (RFC 6066) are implemented. Second, we show that when tags are longer, the TLS Record Protocol meets a new length-hiding authenticated encryption security notion that is stronger than IND-CCA.