web authentication paper from MIT

http://cookies.lcs.mit.edu/pubs/webauth:tr.pdf

Likely a useful read as we design and do security considerations.

 - RL "Bob"

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"Dos and Don'ts of Client Authentication on the Web"

Abstract

Client authentication has been a continuous source of problems on
the Web. Although many well-studied tech-niques exist for authentication,
Web sites continue to use extremely weak authentication schemes,
especially in non-enterprise environments such as store fronts. These
weaknesses often result from careless use of authentica-tors within Web
cookies. Of the twenty-seven sites we investigated, we weakened the client
authentication on two systems, gained unauthorized access on eight, and
extracted the secret key used to mint authenticators from one.

We provide a description of the limitations, require-ments, and security
models specific to Web client authen-tication. This includes the
introduction of the interrog-ative adversary, a surprisingly powerful
adversary that can adaptively query a Web site.

We propose a set of hints for designing a secure client authentication
scheme. Using these hints, we present the design and analysis of a simple
authentication scheme secure against forgeries by the interrogative
adversary. In conjunction with SSL, our scheme is secure against forgeries
by the active adversary.