For example, running the sequence generator through AES rounds. This is keyed, very fast if the hardware supports it, and permutations of types smaller than the block size are collision-free and non-reversible[0] if the AES block is setup suitably.

In other cases, a 128-bit key is simply encrypted (conveniently being the same block size as AES), which allows you to put arbitrary structure inside the exported key.

[0] http://www.jandrewrogers.com/2019/02/12/fast-perfect-hashing...