Cryptology ePrint Archive: Report 2014/585

The SPEKE Protocol Revisited

Feng Hao and Siamak F. Shahandashti

Abstract: The SPEKE protocol is commonly considered one of the classic Password Authenticated Key Exchange (PAKE) schemes. It has been included in international standards (particularly, ISO/IEC 11770-4 and IEEE 1363.2) and deployed in commercial products (e.g., Blackberry). We observe that the original SPEKE specification is subtly different from those defined in the ISO/IEC 11770-4 and IEEE 1363.2 standards. We show that those differences have critical security implications by presenting two new attacks on SPEKE: an impersonation attack and a key-malleability attack. The first attack allows an attacker to impersonate a user without knowing the password by engaging in two parallel sessions with the victim. The second attack allows an attacker to manipulate the session key established between two honest users without being detected. Both attacks are applicable to the original SPEKE scheme, and are only partially addressed in the ISO/IEC 11770-4 and IEEE 1363.2 standards. We highlight deficiencies in both standards and suggest concrete changes.

Category / Keywords: cryptographic protocols / SPEKE, PAKE, IEEE P1362.2, ISO/IEC 11770-4

Date: received 28 Jul 2014, last revised 25 Sep 2014

Contact author: haofeng66 at gmail com

Available format(s): PDF | BibTeX Citation

Note: Updated version to be consistent with the camera-ready version that will appear at SSR'14.

Version: 20140925:213438 (All versions of this report)

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