I've been experimenting with an NTRU open-source C implementation here
I've noticed something (potentionally) strange with a certain set of params: NTRU_EES1087EP2 (defined here).
When generating keys, I seed the DRBG with 64 bytes of entropy (I assume this is enough, as the sample code states that "21 bytes of entropy are needed to instantiate a DRBG with a security strength of 112 bits", and I'm using params for 256-bit security, however if anyone can shed some light onto how this figure is calculated I'd be grateful). However, when I generate the keys - the private key seems to contain long strings of zeros towards the end (see below). Is this normal? It doesn't seem to happen with other parameters.
sample private key... 1718 bytes... concatenated to show the final bytes 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