Authenticated Key Exchange over Bitcoin

Patrick McCorry; Siamak F.  Shahandashti; Dylan Clarke; Feng Hao

Paper 2015/308

Authenticated Key Exchange over Bitcoin

Patrick McCorry, Siamak F. Shahandashti, Dylan Clarke, and Feng Hao

Abstract

Bitcoin is designed to protect user anonymity (or pseudonymity) in a financial transaction, and has been increasingly adopted by major e- commerce websites such as Dell, PayPal and Expedia. While the anonymity of Bitcoin transactions has been extensively studied, little attention has been paid to the security of post-transaction correspondence. In a commercial ap- plication, the merchant and the user often need to engage in follow-up corre- spondence after a Bitcoin transaction is completed, e.g., to acknowledge the receipt of payment, to confirm the billing address, to arrange the product de- livery, to discuss refund and so on. Currently, such follow-up correspondence is typically done in plaintext via email with no guarantee on confidentiality. Obviously, leakage of sensitive data from the correspondence (e.g., billing ad- dress) can trivially compromise the anonymity of Bitcoin users. In this paper, we initiate the first study on how to realise end-to-end secure communica- tion between Bitcoin users in a post-transaction scenario without requiring any trusted third party or additional authentication credentials. This is an important new area that has not been covered by any IEEE or ISO/IEC se- curity standard, as none of the existing PKI-based or password-based AKE schemes are suitable for the purpose. Instead, our idea is to leverage the Bit- coin’s append-only ledger as an additional layer of authentication between previously confirmed transactions. This naturally leads to a new category of AKE protocols that bootstrap trust entirely from the block chain. We call this new category “Bitcoin-based AKE” and present two concrete protocols: one is non-interactive with no forward secrecy, while the other is interactive with additional guarantee of forward secrecy. Finally, we present proof-of-concept prototypes for both protocols with experimental results to demonstrate their practical feasibility.

Note: Accepted to Security Standardisation Research 2015.

Metadata

Available format(s): PDF
Publication info: Published elsewhere. Minor revision. 2nd International Conference on Research in Security Standardisation (SSR'15)
Keywords: Authenticated Key Exchange Bitcoin Diffie-Hellman YAK
Contact author(s): patrick mccorry @ ncl ac uk
History: 2015-09-25: revised; 2015-04-06: received; See all versions
Short URL: https://ia.cr/2015/308
License: CC BY

BibTeX

@misc{cryptoeprint:2015/308,
      author = {Patrick McCorry and Siamak F.  Shahandashti and Dylan Clarke and Feng Hao},
      title = {Authenticated Key Exchange over Bitcoin},
      howpublished = {Cryptology {ePrint} Archive, Paper 2015/308},
      year = {2015},
      url = {https://eprint.iacr.org/2015/308}
}