One brittle, brute force method to do this (RSA-style) a decade ago was LD_PRELOAD vs. the RNG: Phidelius: Constructing Asymmetric Keypairs From Mere Passwords

One brittle, brute force method to do this (RSA-style) a decade ago was LD_PRELOAD vs. the RNG: Phidelius: Constructing Asymmetric Keypairs From Mere Passwords For Fun and PAKE https://dankaminsky.com/2012/01/03/phidelius/ https://dankaminsky.com/2012/01/03/phidelius/ Non-Persistent PGP Keys (2011) https://ritter.vg/blog-non_persistent_pgp.html https://ritter.vg/blog-non_persistent_pgp.html -- Also related: https://github.com/jpf/lokey https://github.com/jpf/lokey, "a tool for converting between cryptographic key formats". Unfortunately it needs maintenance.