I've found this task in the "Introduction Mathematical Cryptography by Jeffrey Hoffstein":
The guidelines for choosing NTRUEncrypt public parameters (N, p, q, d) in-clude the assumption that gcd(N, q) = 1. Suppose instead that Alice takes q = N , where as always, N is an odd prime.
(a) Make a change of variables x = y + 1 in the ring Z[x]/(xN − 1), and show that the NTRU lattice takes a simpler form.
(b) Can you find an efficient way to break NTRU in the case that q = N that does involve lattice reduction? (This appears to be an open problem.)
I have no idea where to start. I didn't find any valuable information on the net. Can anyone offer me literature that explores this particular problem?(Or maybe the step with the change of variables x = y + 1)