croc is a tool I built to easily and securely transfer stuff from one computer to another.

There are many tools that can do this but AFAIK croc is the only tool that is easily installed and used on any platform, and has secure peer-to-peer transferring, and has the capability to resume broken transfers.

Overview

Transmit encrypted data with a code phrase

croc securely transfers data using code phrases - a combination of three random words (mnemonicoded 4 bytes). The code phrase is shared between the sender and the recipient for password authenticated key exchange (PAKE), a cryptographic method to use a shared weak key (the “code phrase”) to generate a strong key for secure end-to-end encryption. By default, a code phrase can only be used once between two parties so an attacker would have a chance of less than 1 in 4 billion to guess the code phrase correctly to steal the data. An attacker with the wrong code phrase will fail the PAKE and the sender will be notified without any data transfering. Only two people with the right code phrase will be able to computers transfer encrypted data through a relay.