Cryptology ePrint Archive: Report 2013/595

Enhanced certificate transparency (how Johnny could encrypt)

Mark D. Ryan

Abstract: The ``certificate authority'' model for authenticating public keys of websites has been attacked in recent years, and several proposals have been made to reinforce it. We develop and extend ``certificate transparency'', a proposal in this direction, so that it efficiently handles certificate revocation. We show how this extension can be used to build a secure end-to-end email or messaging system using PKI with no requirement to trust certificate authorities, or to rely on complex peer-to-peer key-signing arrangements such as PGP. We believe this finally makes end-to-end encrypted email as usable as encrypted web browsing is today, addressing the concerns of a classic paper explaining the difficulties users face in encrypting emails (``Why Johnny can't encrypt'', 1999). Underlying these ideas is a new attacker model appropriate for cloud computing, which we call ``malicious-but-cautious''.

Category / Keywords: applications / public key certificates

Date: received 13 Sep 2013, last revised 13 Sep 2013

Contact author: m d ryan at cs bham ac uk

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Version: 20130914:224639 (All versions of this report)

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