eprintid: 10068168 rev_number: 17 eprint_status: archive userid: 608 dir: disk0/10/06/81/68 datestamp: 2019-02-21 16:01:50 lastmod: 2021-11-04 23:30:11 status_changed: 2019-02-21 16:01:50 type: proceedings_section metadata_visibility: show creators_name: Kulynych, B creators_name: Lueks, W creators_name: Isaakidis, M creators_name: Danezis, G creators_name: Troncoso, C title: ClaimChain: Improving the security and privacy of in-band key distribution for messaging ispublished: pub divisions: UCL divisions: B04 divisions: C05 divisions: F48 note: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. abstract: The social demand for email end-to-end encryption is barely supported bymainstream service providers. Autocryptisa new community-driven open specification for e-mail encryption that attempts to respond to this demand. In Autocrypt the encryption keys are attached directly to messages, and thus the encryption can be implemented by email clients without any collaboration of the providers. The decentralized nature of this in-band key distribution, however, makes it prone to man-in-the-middle attacks and can leak the social graph of users. To address this problem we introduce ClaimChain, a cryptographic construction for privacy-preserving authentication of public keys. Users store claims about their identities and keys, as well as their beliefs about others, in ClaimChains. These chains form authenticated decentralized repositories that enable users to prove the authenticity of both their keys and the keys of their contacts. ClaimChains are encrypted, and therefore protect the stored information, such as keys and contact identities, from prying eyes. At the same time, ClaimChain implements mechanisms to provide strong non-equivocation properties, discouraging malicious actors from distributing conflicting or inauthentic claims. We implemented ClaimChain and we show that it offers reasonable performance, low overhead, and authenticity guarantees. date: 2018-10-15 date_type: published publisher: ACM official_url: https://doi.org/10.1145/3267323.3268947 oa_status: green full_text_type: other language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 1606887 doi: 10.1145/3267323.3268947 isbn_13: 9781450359894 lyricists_name: Danezis, Georges lyricists_name: Isaakidis, Marios lyricists_id: GDANE23 lyricists_id: MISAA08 actors_name: Danezis, Georges actors_name: Turnbull, Sarah actors_id: GDANE23 actors_id: SLTUR91 actors_role: owner actors_role: impersonator full_text_status: public series: Workshop on Privacy in the Electronic Society (WPES') publication: Proceedings of the ACM Conference on Computer and Communications Security volume: 2018 place_of_pub: Toronto, Canada pagerange: 86-103 event_title: Workshop on Privacy in the Electronic Society 2018 (WPES'18) issn: 1543-7221 book_title: Proceeding of Workshop on Privacy in the Electronic Society 2018 (WPES'18) citation: Kulynych, B; Lueks, W; Isaakidis, M; Danezis, G; Troncoso, C; (2018) ClaimChain: Improving the security and privacy of in-band key distribution for messaging. In: Proceeding of Workshop on Privacy in the Electronic Society 2018 (WPES'18). (pp. pp. 86-103). ACM: Toronto, Canada. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10068168/1/1707.06279.pdf