Sat Messenger / RBS

Work in progress

What ?

• It's an *encrypted* short message gateway : email/web <- iridium constellation -> Everywhere on earth
• To reduce cost, a specific encryption is used through the satellite infrastructure part. Of course, one can add final PGP to our code.
• Messages follow destinationemail text :

foo@bar.com I'm fine

• Sat messenger is the satellite part of RBS project : Recovery Base Station. It's a cheaper and encrypted version of University of Berkeley "Rescue Base Station"

"API" refers to rock7 API.

RBS

• There is a info website about this project

Sat Messenger

Somewhere to Internet via sat

Sending a message from everywhere with a sat device, is called "Mobile Originated" (MO). Different codes are available for the "computer" (Raspberry 1 is ok) connected to the sat modem.

• web form run locally (python + twisted)
• command line tool "mo".

Once satellite forwarded the text to the ground, the API can send to an email or to a http POST server. Obviously sending directly to destination email defeat the purpose of privacy. "Mainserver" code can receive the API http POST, decrypt and email the text to destination. (python + twisted)

Internet to Somewhere via sat

It's a "Mobile Terminated case (MT).

• web form (python + twisted)
• command line tool "mt", that make an http POST connection to the API
• rock7 website, but with no encryption.

Like voicemails, to receive messages, one need to start a connection to satellite, ask for queued message and get them one by one.

Hardware

• Satellite communication are based on "Short Burst Data", SBD, message with a 9602 Modem
• All in one version (antenna, modem) can be found at rock7.com. We own a Rockblock +

Embeded version

• Raspberry based

Software

• rock7 documentation is sometimes wrong. i.e serrial communication with the modem use actually the standart 0D 0A end of line.
• makersnake library is a great start for the python way. Altough some URL has changed and some script are not complete. Most of our end user code is heavily based on the awesome works makersnake published.

Crypto

• Iridium SBD Messages are transmitted as is. So if you type clear text, it will be transmitted in... clear text. That's really sucks.
• In the RBS scenario there is no possible communication other than the sat messages and to have very short crypted messages (50 characters for 0.05 euro) we use some short stream cipher and hash function.
• There is probably better choice, but the goal was to encrypt, we welcome crypto experts to improve this part.