Debian 9 installed libsodium

To here view the latest version. As now the latest version number 1.0.18. Here are the version, for example.

Download, compile and install:

wget https://download.libsodium.org/libsodium/releases/libsodium-1.0.18.tar.gz
tar xf libsodium-1.0.18.tar.gz
cd libsodium-1.0.18
./configure
make -j2
make install
ldconfig

Delete the source code to compile and install left:

cd ..
rm libsodium-1.0.18.tar.gz
rm -r libsodium-1.0.18