International Association for Cryptologic Research

International Association
for Cryptologic Research


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

Kenneth G. Paterson
Gaven J. Watson
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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.
  title={Plaintext-Dependent Decryption: A Formal Security Treatment of SSH-CTR},
  booktitle={IACR Eprint archive},
  keywords={secret-key cryptography /},
  note={A short version of this paper is to appear in the proceedings of Eurocrypt 2010. This is the full version. 14666 received 23 Feb 2010, last revised 26 Feb 2010},
  author={Kenneth G. Paterson and Gaven J. Watson},