EAP SHA256-SRP6a Authentication Protocol
draft-eap-sha256-srp6a-00

Abstract

This document describes an authentication protocol intended for Internet applications which may require a robust and non-leaky exchange of credentials even under adverse network conditions. The protocol has the ability to recover from packet loss during the authentication process, as for example, should the Internet application use the UDP transport protocol under lossy network conditions. It does so by allowing the retransmission of lost packets during authentication. The protocol follows the Extensible Authentication Protocol (RFC 3748 and RFC 5247) framework, which allows for the use of multiple authentication mechanisms. It utilizes Secure Remote Password protocol (RFC 2945), with strong, password-based cryptographic hashing. It utilizes the Secure Hashing Algorithm message digest algorithm as the hashing mechanism. The authentication protocol allows for one Server and one or more Clients. Where multiple Clients exist, each may communicate only with the Server. Clients initiate the authentication exchange process. Until the authentication completes successfully, the Server and Client ignore/discard any packets except those supporting the authentication process. The authentication algorithm is based on a username/password or passphrase pair. These are used to generate secure ephemeral keys. The Server has a store of all valid usernames and password hashes. Each Client stores its own username and password. The authentication algorithm provides for each side to prove to the other that it has a valid username/password or passphrase pair, in a way that a third-party monitoring the transactions could not use intercepted information to later successfully authenticate. This mutual authentication exchange consists of several pairs of interactions. The first is a request for authentication by the Client, containing the Client name, to which the Server responds with a challenge for its identity. The Client responds with the Server name for verification purposes. Thereafter, Client and Server each exchange three values consisting of password salts, ephemeral public keys, and hash values. These are generated and verified by Client and Server in accordance with SRP against the stored password/passphrase hashes. While any step in the process may be repeated to provide for dropped packets should a response not be received, the authentication process is terminated by any incorrect value received in any response. Multicast UDP authentication is also supported, with certain limitations.

Authors

Sergio Ammirata
Gijs Peskens
Brad Gilmer
John Iacovelli

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)