contego/README.md

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## Cryptographic specifications

The initial key exchange is performed with elliptic-curve Diffie-Hellman. General data exchange is encrypted with AES-GCM. During regular communication payloads are Base64 encoded before being encrypted to prevent delimiter conflicts. SHA-256 hashes of files are compared to ensure data integrity.

## Cellular networks

Most cellular ISP's tend to block port forwarding on CGNAT level, which makes it impossible to create inbound connections to such network without a VPN. Luckily many consumer VPNs and self-hosted solutions make port forwarding a trivial task. This is the main reason why the client must fetch information about the public IP from an external service (https://ipinfo.io/ip for IPv4 and https://ipv6.icanhazip.com for IPv6). 

## Usage

Check [releases](https://github.com/17ms/contego/releases) for an up-to-date executables or build from source with `cargo build --release`.

### Server

```
Usage: contego host [OPTIONS] --key <KEY> <--source <SOURCE>|--files <FILES>...>

Options:
  -k, --key <KEY>              Access key
  -s, --source <SOURCE>        Path to a source file (alternative to --files)
  -f, --files <FILES>...       Paths to shareable files (alternative to --source)
  -p, --port <PORT>            Host port [default: 8080]
  -6, --ipv6                   IPv6 instead of IPv4
  -c, --chunksize <CHUNKSIZE>  Transmit chunksize in bytes [default: 8192]
  -l, --local                  Host locally
  -h, --help                   Print help

```

### Client

```
Usage: contego connect --addr <ADDR> --out <OUT> --key <KEY>

Options:
  -a, --addr <ADDR>  IP address of the instance
  -o, --out <OUT>    Path to an output folder
  -k, --key <KEY>    Access key
  -h, --help         Print help
```