A Domain Extender for the Ideal Cipher

Provided by: University of Luton
Topic: Security
Format: PDF
The authors describe the first domain extender for ideal ciphers, i.e. they show a construction that is indifferentiable from a 2n-bit ideal cipher, given a n-bit ideal cipher. Their construction is based on a 3-round Feistel, and is more efficient than first building a n-bit random oracle from a n-bit ideal cipher (as in [9]) and then a 2n-bit ideal cipher from a n-bit random oracle (as in [10], using a 6-round feistel). They also show that 2 rounds are not enough for in-differentiability by exhibiting a simple attack.

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