On the (Im)possibility of Basing Oblivious Transfer and Bit Commitment on Weakened Security Assumptions

We consider the problem of basing Oblivious Transfer (OT) and Bit Commitment (BC), with information theoretic security, on seemingly weaker primitives. We introduce a general model for describing such primitives, called Weak Generic Transfer (WGT). This model includes as important special cases Weak Oblivious Transfer (WOT), where both the sender and receiver may learn too much about the other party’s input, and a new, more realistic model of noisy channels, called unfair noisy channels. An unfair noisy channel has a known range of possible noise levels; protocols must work for any level within this range against adversaries who know the actual noise level. We give a precise characterization for when one can base OT on WOT. When the deviation of the WOT from the ideal is above a certain threshold, we show that no information-theoretic reductions from OT (even against passive adversaries) and BC exist; when the deviation is below this threshold, we give a reduction from OT (and hence ...

• Type: Conference
• Year: 1999
• Where: EUROCRYPT
• Authors: Ivan Damgård, Joe Kilian, Louis Salvail
• Keywords: Bit Commitment, Cryptology, EUROCRYPT 1999, Oblivious Transfer, Unfair Noisy Channels