IACR News item: 20 February 2013
Grégory Landais, Jean-Pierre Tillich
ePrint Reportreplaces Goppa codes by convolutional codes. This modification is supposed to make
structural attacks more difficult since the public generator matrix of this scheme contains
large parts which are generated completely at random. They proposed two schemes of this
kind, one of them consists in taking a Goppa code and extending it by adding a generator matrix of
a time varying convolutional code. We show here that this scheme can be successfully attacked by looking
for low-weight codewords in the public code of this scheme and using it to unravel the convolutional part.
It remains to break the Goppa part of this scheme which can be done in less than a day of computation in
the case at hand.
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