`croc` is a tool that allows any two computers to simply and securely transfer files and folders. AFAIK, *croc* is the only CLI file-transfer tool that does **all** of the following:
- allows **any two computers** to transfer data (using a relay)
There is an Android version for croc at https://github.com/howeyc/crocgui which is available at for download at https://f-droid.org/en/packages/com.github.howeyc.crocgui/
The code phrase is used to establish password-authenticated key agreement ([PAKE](https://en.wikipedia.org/wiki/Password-authenticated_key_agreement)) which generates a secret key for the sender and recipient to use for end-to-end encryption.
There are a number of configurable options (see `--help`). A set of options (like custom relay, ports, and code phrase) can be set using `--remember`.
By default, croc will prompt whether to overwrite a file. You can automatically overwrite files by using the `--overwrite` flag (recipient only). For example, receive a file to automatically overwrite:
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` will automatically approve the transfer and pipe it out to `stdout`.
You can choose from several different elliptic curves to use for encryption by using the `--curve` flag. Only the recipient can choose the curve. For example, receive a file using the P-521 curve:
Available curves are P-256, P-348, P-521 and SIEC. SIEC is the default curve used, it is a lesser known curve that belongs to a class of "super-isolated" curves which has security that does not reduce to the security of curves around it. (Scholl, Travis. Experimental Mathematics 28.4 (2019): 385-397)
The relay is needed to staple the parallel incoming and outgoing connections. By default, `croc` uses a public relay but you can also run your own relay:
By default it uses TCP ports 9009-9013. Make sure to open those up. You can customized the ports (e.g. `croc relay --ports 1111,1112`), but you must have a minimum of **2** ports for the relay. The first port is for communication and the subsequent ports are used for the multiplexed data transfer.
You can send files using your relay by entering `--relay` to change the relay that you are using if you want to custom host your own.
Note, when sending, you only need to include the first port (the communication port). The subsequent ports for data transfer will be transmitted back to the user from the relay.
#### Self-host relay (docker)
If it's easier you can also run a relay with Docker:
Note: when including `--pass YOURPASSWORD` you can instead pass a file with the password, e.g. `--pass FILEWITHPASSWORD`.
## License
MIT
## Acknowledgements
`croc` has gone 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](http://ctt.ec/Rq054)).
Thanks [@warner](https://github.com/warner) for the [idea](https://github.com/warner/magic-wormhole), [@tscholl2](https://github.com/tscholl2) for the [encryption gists](https://gist.github.com/tscholl2/dc7dc15dc132ea70a98e8542fefffa28), [@skorokithakis](https://github.com/skorokithakis) for [code on proxying two connections](https://www.stavros.io/posts/proxying-two-connections-go/). Finally thanks for making pull requests [@maximbaz](https://github.com/maximbaz), [@meyermarcel](https://github.com/meyermarcel), [@Girbons](https://github.com/Girbons), [@techtide](https://github.com/techtide), [@heymatthew](https://github.com/heymatthew), [@Lunsford94](https://github.com/Lunsford94), [@lummie](https://github.com/lummie), [@jesuiscamille](https://github.com/jesuiscamille), [@threefjord](https://github.com/threefjord), [@marcossegovia](https://github.com/marcossegovia), [@csleong98](https://github.com/csleong98), [@afotescu](https://github.com/afotescu), [@callmefever](https://github.com/callmefever), [@El-JojA](https://github.com/El-JojA), [@anatolyyyyyy](https://github.com/anatolyyyyyy), [@goggle](https://github.com/goggle), [@smileboywtu](https://github.com/smileboywtu), [@nicolashardy](https://github.com/nicolashardy), [@fbartels](https://github.com/fbartels), [@rkuprov](https://github.com/rkuprov), [@hreese](https://github.com/hreese), [@xenrox](https://github.com/xenrox) and [Ipar](https://github.com/lpar)!
