We provide new constructions for Luby-Rackoff block ciphers which are efficient in terms of computations and key material
used. Next, we show that we can make some security guarantees for Luby-Rackoff block ciphers under much weaker and more practical
assumptions about the underlying function; namely, that the underlying function is a secure Message Authentication Code. Finally,
we provide a SHA-1 based example block cipher called Sha-zam.
Work done while this author was at Lucent Technologies