Abstract:
In a paper from EuroCrypt'99, Damgård, Kilian and Salvail
show various positive and negative results on constructing Bit Commitment
(BC) and Oblivious Transfer (OT) from Unfair Noisy Channels (UNC), i.e.,
binary symmetric channels where the error rate is only known to be in a
certain interval
![$[\gamma ..\delta]$](Abs/img1.gif)
and can be chosen adversarily. They also
introduce a related primitive called 
. We prove in this paper
that any OT protocol that can be constructed based on a and is
secure against a passive adversary can be transformed using a generic
``compiler'' into an OT protocol based on a 
which is secure against an
active adversary. Apart from making positive results easier to prove in
general, this also allows correcting a problem in the EuroCrypt'99 paper:
There, a positive result was claimed on constructing from UNC an OT that is
secure against active cheating. We point out that the proof sketch given for
this was incomplete, and we show that a correct proof of a much stronger
result follows from our general compilation result and a new technique for
transforming between weaker versions of OT with different
parameters.
and can be chosen adversarily. They also
introduce a related primitive called . We prove in this paper
that any OT protocol that can be constructed based on a and is
secure against a passive adversary can be transformed using a generic
``compiler'' into an OT protocol based on a which is secure against an
active adversary. Apart from making positive results easier to prove in
general, this also allows correcting a problem in the EuroCrypt'99 paper:
There, a positive result was claimed on constructing from UNC an OT that is
secure against active cheating. We point out that the proof sketch given for
this was incomplete, and we show that a correct proof of a much stronger
result follows from our general compilation result and a new technique for
transforming between weaker versions of OT with different
parameters.Available as PostScript, PDF.