The effort for P2P private talk over GSM-FR compressed voice channel
PairPhone is the crossplatform testing software provides p2p speech encryption duplexes over GSM compressed voice call. The modern cryptography with about 128-bit protection level is use Triple Diffie- Hellman initial key exchange with elliptic curve 25519 and SHA3 Keccak 1600/576 Sponge Duplexing based cipher, hash, MAC, SPRNG. Each call's setup provide PSF for encryption and ID’s protecting, UKS and KCI resistance. Primary authentication using shared password and comparing of secret's fingerprint, hidden notification of enforcement are available. Devices can be paired during first ‘guest’ call, certificate for this contact will be added to the address book. PairPhone uses special ‘military’ style of cryptographic solutions suitable for low data rate with permanent BER such as error spreading resistance, probabilistic flow authentication and short exchanged values. The goal of the project is specially designed pseudo speech modem with small distortion of baseband signal passing over tandem of GSM FR codecs uses in real GSM voice communication. Modem achieves 1200 bps data rate with less then 1% bit error rate and quick on-the-fly synchronizing after less than 200 ms of streaming. Using the voice calls instead CSD avoid the user profiling and prevents the targeted collection of metadata. The app is maked by GCC (*nix) or mingw (Windows) (just follow ‘make’) and does not require libraries except libasound2-dev. The binary file for Linux and Windows is statically linked, fully portable, can be run from removable media or TrueCrypt-container and write to address book file in the working folder only during pairing. Source code have low-level C style and ready to embedding into hardware (at least 50 MIPS and floating points arithmetic requires , i.e. Cortex F4). The testing application can be run on a PC (1GHz Celeron) and requires 2 hardware audio devices (e.g., onboard audio plus installed USB audio or bluetooth headset) and uses an analog audio interface to connect with GSM link. We used evaluation boards for GSM-modules Quectel M66 providing the lock the GSM FR codec (just one that must be supported in any cells) and advanced audio settings via the engineering menu. If digital audio bus will be used the modem can work at 8KHz samples rate instead of 48 kHz thus reduce the computational complexity of about 5 times.
Web page: http://torfone.org/pairphone
Docs: http://torfone.org/download/pp1a_doc.pdf
Binaries(Windows, Linux): http://torfone.org/download/pp1a_bin.zip
Contact: «Van Gegel» torfone@ukr.net