pseudorandom permutation造句

Michael Luby and Charles Rackoff showed that a " strong " pseudorandom permutation can be built from a pseudorandom function using a Luby Rackoff construction which is built using a Feistel cipher.
As cipher algorithms are designed to be indistinguishable from a pseudorandom permutation without knowing the key, the presence of data on the encrypted volume is also undetectable unless there are known weaknesses in the cipher.
So the problem of FPE is to generate a pseudorandom permutation from a secret key, in such a way that the computation time for a single value is small ( ideally constant, but most importantly smaller than O ( N ) ).
When the underlying block cipher is a strong pseudorandom permutation ( PRP ) then on the sector level the scheme is a tweakable PRP . One problem is that in order to decrypt \ scriptstyle P _ 0 one must sequentially pass over all the data twice.
If there is a set " M " of allowed values within the domain of a pseudorandom permutation P ( for example P can be a block cipher like AES ), an FPE algorithm can be created from the block cipher by repeatedly applying the block cipher until the result is one of the allowed values ( within " M " ).
It's difficult to find pseudorandom permutation in a sentence. 用pseudorandom permutation造句挺难的