Cold Signing 
I'm looking for a pure Rust crate to use as the offline wallet component of this workflow: https://monerodocs.org/cold-storage/offline-transaction-signing/ I'm sharing this as a reference, but I'm not expecting this library to do more than the cryptography required. 

I understand that this crate can a) create the offline wallet key material; b) deserialize the unsigned transaction; c) recover outputs from the read-only wallet. Based on my superficial understanding of the protocol, I'm unclear on what's involved in "sign_transfer" and "export_key_images". 

If this isn't on your roadmap, I would appreciate some guidance on how one might implement this. I may be able to contribute after doing my homework if need be. 