I. Zs. Berta, L. Buttyán, I. Vajda
Mitigating the Untrusted Terminal Problem Using Conditional Signatures
Proceedings of International Conference on Information Technology ITCC 2004, IEEE, 2004, IEEE, Las Vegas, NV, USA, April.
abstract We study the problem of how a user at an untrusted terminal can generate digital signatures with the help of a smart card. This problem may arise in many practical applications; an example would be a user generating an electronic check at a merchant's terminal in a shop. The danger is that after receiving the PIN code of the card from the user, the terminal can obtain a signature from the card on an arbitrarily chosen document, that is different from the one displayed on the screen and confirmed by the user. We propose a solution to this problem which is based on a new concept called conditional signature. This leads to a new paradigm where digital signatures are not considered as non-repudiable proofs, at least until a short deadline.