0b4640a508
This typo doesn't seem to cause any issue because according to the code in vanilla NaCl the first crypto_box_ZEROBYTES (for encryption) and crypto_box_BOXZEROBYTES (for decryption) of the array passed to the crypto_box*() functions don't need to be zero for it to work. The documentation however clearly states that they need to be zero which means they need to be zero.
With the rise of governmental monitoring programs, Tox, a FOSS initiative, aims to be an easy to use, all-in-one communication platform that ensures their users full privacy and secure message delivery.
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The Complex Stuff:
UDP vs. TCP
Tox must use UDP simply because hole punching with TCP is not as reliable. However, Tox does use TCP relays as a fallback if it encounters a firewall that prevents UDP hole punching.
Connecting & Communicating
Every peer is represented as a byte string (the public key [Tox ID] of the peer). By using torrent-style DHT, peers can find the IP of other peers by using their Tox ID. Once the IP is obtained, peers can initiate a secure connection with each other. Once the connection is made, peers can exchange messages, send files, start video chats, etc. using encrypted communications.
Current build status: 
Q&A:
What are your goals of Tox?
We want Tox to be as simple as possible while remaining as secure as possible.
Why are you doing this? There are already a bunch of free Skype alternatives.
The goal of this project is to create a configuration-free P2P Skype replacement. Configuration-free means that the user will simply have to open the program and without any account configuration will be capable of adding people to his or her's friends list and start conversing with them. There are many so-called Skype replacements and all of them are either hard to configure for the normal user or suffer from being way too centralized.