** Abstract: ** The notion of a ``proof of knowledge,'' suggested by
Goldwasser, Micali and Rackoff, has been used in many works as a tool for the
construction of cryptographic protocols and other schemes. Yet the commonly
cited formalizations of this notion are unsatisfactory and in particular
inadequate for some of the applications in which they are used. Consequently,
new researchers keep getting misled by existing literature. The purpose of
this paper is to indicate the source of these problems and suggest a definition
which resolves them.

** Ref:** Extended abstract in Advances in Cryptology - Crypto 92
Proceedings, Lecture Notes in Computer Science Vol. 740, E. Brickell ed,
Springer-Verlag, 1993. Full paper available below.

** Full paper: ** Available as compressed
postscript, postscript, or
pdf. ( Help if this doesn't work).

** Abstract: ** We investigate extending the notion of a proof of knowledge
to a proof of the ability to perform some computational task. We provide some
definitions and protocols for this purpose.

** Ref:** Manuscript, August 1992. Available below.

** Full paper: ** Available as compressed
postscript, postscript, or
pdf. ( Help if this doesn't work).