I decided that there should be a simpler way and I created unity.libsodium, a plugin that helps you to use libsodium in your Unity3d projects in a clear and easy way and works in iOS, Android, OSX, Windows, Android projects.
- prebuilt library are maintained by prebuilt-libsodium
- libsodium 1.0.20-RELEASE
 
using #{version} for versioning.
"com.netpyoung.libsodium": "https://github.com/netpyoung/unity.libsodium.git?path=unity.libsodium/Assets/unity.libsodium#0.2.3"- check unity.libsodium.test
/*
 * ISC License
 *
 * Copyright (c) 2013-2018
 * Frank Denis <j at pureftpd dot org>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
- https://github.com/jedisct1/libsodium/tree/master/src/libsodium/include/sodium/
- https://github.com/joshjdevl/libsodium-jni/blob/master/src/main/java/org/libsodium/jni/SodiumJNI.java
- https://github.com/terl/lazysodium-android
- https://github.com/adamcaudill/libsodium-net/blob/master/libsodium-net/SodiumLibrary.cs
- https://github.com/microsoft/ClangSharp