curl https://getcroc.schollz.com | bash

croc is a tool that allows any two computers to simply and securely transfer files and folders. 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 (through a relay), allows multiple files, and has the capability to resume broken transfers.

For more information on how croc works, see my blog post.

Install

Download the latest release for your system, or install a release from the command-line:

$ curl https://getcroc.schollz.com | bash

Or, you can install Go and build from source (requires Go 1.11+):

go get github.com/schollz/croc

Usage

To send a file, simply do:

$ croc send FILE

Them to receive the file, you can just do

$ croc [code-phrase]

Custom code phrase

You can send with your own code phrase (must be more than 4 characters).

$ croc send --code [code phrase] [filename]

Use locally

croc automatically will attempt to start a local connection on your LAN to transfer the file much faster. It uses peer discovery, basically broadcasting a message on the local subnet to see if another croc user wants to receive the file. croc will utilize the first incoming connection from either the local network or the public relay and follow through with PAKE.

You can change this behavior by forcing croc to use only local connections (--local) or force to use the public relay only (--no-local):

$ croc --local/--no-local send [filename]

Using pipes - stdin and stdout

You can easily use croc in pipes when you need to send data through stdin or get data from stdout. To send you can just use pipes:

$ cat [filename] | croc send

In this case croc will automatically use the stdin data and send and assign a filename like "croc-stdin-123456789". To receive to stdout at you can always just use the -yes and -stdout flags which will automatically approve the transfer and pipe it out to stdout.

$ croc -yes -stdout [code phrase] > out

All of the other text printed to the console is going to stderr so it will not interfere with the message going to stdout.

Self-host relay

The relay is needed to staple the parallel incoming and outgoing connections. The relay temporarily stores connection information and the encrypted meta information. The default uses a public relay at, croc4.schollz.com. You can also run your own relay, it is very easy, just run:

$ croc relay

Make sure to open up TCP ports (see croc relay --help for which ports to open). Relays can also be customized to which elliptic curve they will use (default is siec).

You can send files using your relay by entering -addr to change the relay that you are using if you want to custom host your own.

$ croc -addr "myrelay.example.com" send [filename]

Configuration file

You can also make some paramters static by using a configuration file. To get started with the config file just do

$ croc config

which will generate the file that you can edit. Any changes you make to the configuration file will be applied before the command-line flags, if any.

License

MIT

Acknowledgements

croc has been through many iterations, and I am awed by all the great contributions! If you feel like contributing, in any way, by all means you can send an Issue, a PR, ask a question, or tweet me (@yakczar).

Thanks...

• ...@warner for the idea.
• ...@tscholl2 for the encryption gists.
• ...@skorokithakis for code on proxying two connections.
• ...for making pull requests @Girbons, @techtide, @heymatthew, @Lunsford94, @lummie, @jesuiscamille, @threefjord, @marcossegovia, @csleong98, @afotescu, @callmefever, @El-JojA, @anatolyyyyyy, @goggle, @smileboywtu, @nicolashardy!