Cryptoint is a library created by Daniel J. Bernstein.
It's public-domain code used in SUPERCOP/libntruprime/libmceliece/...
To Dq is imported from https://libntruprime.cr.yp.to/libntruprime-20241021/cryptoint.html.

Description from the author e.g. here:
 - https://cr.yp.to/talks/2024.07.22/slides-djb-20240722-snippets-4x3.pdf
