Chapter

Advances in Cryptology – EUROCRYPT 2010

Volume 6110 of the series Lecture Notes in Computer Science pp 345-361

Plaintext-Dependent Decryption: A Formal Security Treatment of SSH-CTR

  • Kenneth G. PatersonAffiliated withInformation Security Group, Royal Holloway, University of London, Egham
  • , Gaven J. WatsonAffiliated withInformation Security Group, Royal Holloway, University of London, Egham

Abstract

This paper presents a formal security analysis of SSH in counter mode in a security model that accurately captures the capabilities of real-world attackers, as well as security-relevant features of the SSH specifications and the OpenSSH implementation of SSH. Under reasonable assumptions on the block cipher and MAC algorithms used to construct the SSH Binary Packet Protocol (BPP), we are able to show that the SSH BPP meets a strong and appropriate notion of security: indistinguishability under buffered, stateful chosen-ciphertext attacks. This result helps to bridge the gap between the existing security analysis of the SSH BPP by Bellare et al. and the recently discovered attacks against the SSH BPP by Albrecht et al. which partially invalidate that analysis.

Keywords

SSH counter mode security proof