Two Cans Voice Encryption
This application permits secure, encrypted conversations between two telephone users, without using the internet. It works on a PC connected to an ordinary phone line, or in a smartphone on the cell phone network. Because it does not need the internet, it can work where no internet is available or where internet costs are high.
Two Cans includes a modem implemented in software. The soft modem creates a digital connection between the two phones. Standard voice encryption mechanisms are used across this soft modem connection. I am developing a gateway for interoperability among two cans users and internet phone users implementing SRTP or ZRTP; the gateway must run on a PC or other computer connected to the network and to an ordinary phone line.
To thwart man-in-the-middle attacks, two cans may employ the ZRTP short authentication strings, or it may use more conventional certificates.
Two cans also can be used for secure document transmission over the voice channel.
Several codecs and modems are being developed. Note that specification of a connection requires two codec types: one for digitization of speech, and the other to convert the encrypted data link back into audio form for transmission over the voice channel. Of course, depending on the platform, one or both codec types may restricted to available implementations. On a given link or connection, pre-existing hardware and software may strongly suggest certain specific combinations.
Two cans should be very secure. There are two main attack mechanisms: compromising the cell phone (or PC) itself, and man-in-the-middle attacks. A future project will focus on hardening the cell phones. Meanwhile, proper use of certificates should (absent physical or software compromise of the phone itself) minimize the risk of MITM attacks.
I expect to make two cans available under GPL 3.
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