Paper 2010/095

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

Kenneth G. Paterson and Gaven J. Watson


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.

Available format(s)
Secret-key cryptography
Publication info
Published elsewhere. A short version of this paper is to appear in the proceedings of Eurocrypt 2010. This is the full version.
Contact author(s)
kenny paterson @ rhul ac uk
2010-02-26: revised
2010-02-25: received
See all versions
Short URL
Creative Commons Attribution


      author = {Kenneth G.  Paterson and Gaven J.  Watson},
      title = {Plaintext-Dependent Decryption: A Formal Security Treatment of SSH-CTR},
      howpublished = {Cryptology ePrint Archive, Paper 2010/095},
      year = {2010},
      note = {\url{}},
      url = {}
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