Install libnacl-dev by entering the following commands in the terminal:
sudo apt update sudo apt install libnacl-dev
High-speed software library for network communication
NaCl (pronounced "salt") is a new easy-to-use high-speed software library for network communication, encryption, decryption, signatures, etc. NaCl's goal is to provide all of the core operations needed to build higher-level cryptographic tools. This package contains header and library files needed for software development that makes use of NaCl.