cryptochat

Encrypted P2P chat over ICMP (Internet Control Message Protocol).

I strongly advise you to pick a high-entropy encryption key to avoid the possibility of brute-force attacks.

Uses raw-socket for ICMP handling and terminal-colors to spice it up a bit.

Install and usage

Make sure you have node 0.10.x (tip: use n) and then install the package globally with sudo.

sudo npm install -g cryptochat

Three variants of cryptochat are available depending on your use case:

• Send and receive messages

  $ sudo cryptochat <ip> <encryption_key>

• Receive messages

  $ sudo cryptochat server <encryption_key>

• Send messages

  $ sudo cryptochat client <ip> <encryption_key>

Because it relies on stdin for input, it is possible to use pipes to send data:

cat cryptochat.js | sudo cryptochat client <ip> <encryption_key>

ICMP Echo request format

bits 0-7	bits 8-15	bits 16-31
type = 0x08	code = 0x00	checksum
identifier		sequence number
payload

The message data is attached as the ICMP payload.

Message

Messages are piped from stdin and split into payload packages, which are encrypted and sent as ICMP Echo requests. The payload size per request is currently set to 32 bytes. The first byte is the length of the message and the rest is the message itself.

The first request contains a salt and an initialization vector needed to decrypt the payloads.

byte 0	bytes 1-15	bytes 16-31
0x3e	salt	initialization vector

An "end" request is sent in order for the receiver to know when a message is completed. The end request has the following format:

byte 0	bytes 1-31
0x3e	0xffffffff...

When the end request is received, the full message is printed to the screen.

Contribute

As always, contributions are much appreciated.