acmo0

Hello, I implemented [Grain-128AEADv2](https://csrc.nist.gov/CSRC/media/Projects/lightweight-cryptography/documents/finalist-round/updated-spec-doc/grain-128aead-spec-final.pdf) (one of the NIST lightweight cryptography finalist). It works without the standard library and even without alloc by disabling the `vec` default feature. I tried to...