Libsodium is a modern, portable, easy to use crypto library. Sodium is a new, easy-to-use software library for encryption, decryption, signatures, password hashing and more.
It is a portable, cross-compilable, installable, packageable fork of NaCl, with a compatible API, and an extended API to improve usability even further. Its goal is to provide all of the core operations needed to build higher-level cryptographic tools.
The documentation is available on Gitbook and built from the libsodium-doc repository:
Integrity Checking Libsodium
The integrity checking instructions (including the signing key for it) are available in the installation section of the documentation.