Asignify tool is heavily inspired by signify used in OpenBSD. However, the main
goal of this project is to define high level API for signing files, validating
signatures and encrypting using public keys cryptography. Asignify is designed
to be portable and self-contained with zero external dependencies. It uses
blake2b as the hash function and ed25519 implementation from tweetnacl.

Key features:

- Zero dependencies (libc and C compiler are likely required though), so it
  could be easily used in embedded systems.
- Modern cryptography primitives (ed25519, blake2 and sha512 namely).
- Ability to encrypt files with the same keys using curve25519 based cryptobox.
- Protecting secret keys by passwords using PBKDF2-BLAKE2 routine.
- Asignify can convert ssh ed25519 private keys to the native format and verify
  signatures using just ssh ed25519 public keys (without intermediate
  conversions).
- Asignify provides high level API for application developers for signing,
  verifying, encrypting and keys generation.
- All keys, signatures and encrypted files contain version information allowing
  to change cryptographical primitives in the future without loosing of
  backward compatibility.

WWW: https://github.com/vstakhov/asignify/