Using human interactive proofs to secure human-machine interactions via untrusted intermediaries

Abstract

This paper explores ways in which Human Interactive Proofs (HIPs), i.e. problems which are easy for humans to solve but are intractable for computers, can be used to improve the security of human-machine interactions. The particular focus of this paper is the case where these interactions take place via an untrusted intermediary device, and where the use of HIPs can be used to establish a secure channel between the human and target machine. A number of application scenarios of this general type are considered, and in each case the possible use of HIPs to improve interaction security is explored. © 2009 Springer-Verlag Berlin Heidelberg.