We revisit the question of constructing an ideal cipher
from a random oracle.
Coron et al.~(Journal of Cryptology, 2014) proved that a 14-round Feistel network using random,
independent,
keyed round functions
is indifferentiable from an ideal cipher, thus demonstrating the feasibility
of such a construction.
Left unresolved is the best possible efficiency of the transformation.
We improve upon the result of Coron et al.\ and show that
10 rounds suffice.
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