Just started. Not ready yet.

You have a large folder called stuff. You want to send it to a friend over the intertubes, but there's a problem: both of you are behind NAT and are too lazy (or unable) to forward ports. What are your options?

• FTP on my server: Requires giving the sender an account and takes longer (has to finish uploading before you start the download). Also wastes the server's bandwidth.
• Public services where you upload via the browser while they bombard you with ads: Still slower for the same reason as FTP, but also annoying.
• Create a torrent without a tracker (or a private tracker).

BitTorrent is probably the best solution because it's direct and works behind NAT. You can try creating your own torrent and setting up a private tracker or trying to add a peer directly. Remember to turn off peer discovery such as DHT or someone unexpected could download off you.

I propose a solution that is designed specifically for person-to-person transfers of large files & folders.

TODO: Consider expanding the scope to support multiple peers. It would have the following implications:

• Chunk-based transfers with chunk hash verification.
• How to control who can join the share?
• Peers can all see each other's IPs.
• Possible detection as a P2P service by traffic shapers? Not if they only target specific known protocols.
• The only benefit is a P2P transfer model which becomes favorable with a large number of peers.
• Too similar to BitTorrent.

./vortex share stuff vortex1.virtivia.com
Setting up a listener
Attempting to portmap with UPnP: Success
Connecting to vortex1.virtivia.com:27805
Registering with the hub server
Got share code RZSCH2
Secret share key for folder 'stuff': RZSCH2-SUvBJFNoA9RsF7-yFcdzkwv5MFeyYXzxCc74xiTo3Y=
Ready to transfer

Receiver command: ./vortex get [path] RZSCH2-SUvBJFNoA9RsF7-yFcdzkwv5MFeyYXzxCc74xiTo3Y= vortex1.virtivia.com

Current receivers:
==================
None

./vortex get ~/Downloads/ RZSCH2-yFcdzkwv5MFeyYXzxCc74xiTo3Y= vortex1.virtivia.com
Connecting to vortex1.virtivia.com:27805
Found host for share code RZSCH2
Connecting to share host: 24.42.139.77:45934
Waiting for the host's public key
Host's public key matches the SHA1 hash 'yFcdzkwv5MFeyYXzxCc74xiTo3Y='
Authenticating with share key 'SUvBJFNoA9RsF7'
Downloading to /Users/Pavel/Downloads/stuff/
[subfolder/moo.txt] [59 KB]
[blah.mkv] [25.1 / 97.8 MB (25%) @ 1.3 MB/s]

• All data, including the manifest, is transmitted in encrypted form, so nobody except the sharer and the receiver can figure out exactly what is being transmitted, aside from possibly being able to calculate its size. Dumping random junk on the wire to prevent this is not currently in scope. The only data transmitted in plaintext is: share code, public keys, and sharer's IP address & port.
• The SHA1 hash of the sharer's public key is included as part of the share key to prevent man-in-the-middle attacks.
• Upon connecting to the sharer, the receiver provides its public key. The sharer then securely generates 256 bits which become the AES key for the remainder of the session, and sends this key encrypted via RSA using the receiver's public key.

To be determined. The remaining approach is to stream the data through a server that is not behind NAT, but this is costly for whomever owns the server. People could run their own servers and auth to them. Server auth may be in phase 2 and optional (if the server is to be used as a middleman).