Wireless GSM telephony is expensive with high smartphone prices, long term mobile plans and accruing calling costs. Calls are prone to be recorded and monitored. Voice quality is poor due high compression ratios. Not to forget the contract that is signed containing personal info.
WiFi Crypto Phone offers a choice. A new method of wireless telephony that is innovative. A low cost GSM alternative phone. The answer to privacy deficient smartphones.
Confidentiality through voice encryption is a standard feature.
It has the stylish looks of a smartphone, the mic/speaker marks of a good old land line phone and is the lightest of mobile phones. Assembled are only essential components. Glass screen and keyboard were not needed. Elegant operation with two buttons on the left for navigating the phone book and another one on the right to call.
8000 Hz 8-bit PCM 64 kbps sampled raw voice data is reduced to 32 kbps via 4-bit ADPCM compression, which accounts for good voice quality. Finally triple DES encryption is applied to have a stream of P2P encrypted voice data packets that are sent through the internet.
Integrated is a secure chip AT90SC1818CT (obtainable only by signing a NDA) that is the core component for key generation and real time voice encryption. Session key is exchanged using 2048 bit RSA asymmetric key encryption. Voice data is encrypted with triple DES and transmitted as CBC stream between WiFi phones.
The secure chip is input with both internal raw voice data of 64 kbps and the encrypted data of 32 kbps received from other phone. It compresses and encrypts the raw data and decrypts and decompresses the encrypted data. It then outputs decoded raw 64 kbps data for listening and encrypted 32 kbps data to be sent to other phone. This cycle repeats every 8ms. Overall data rate to/from secure chip is about 100 Mbyte/h. 1000 triple DES operations are performed every second. Cipher Block Chaining is utilized where a cycle counter is being used as IV and also XOR'ed onto the session key. UDP packets carry a bunch of data of 13 cycles for 104ms length to ensure low latency.
2048-bit RSA key generation and storage happens within secure chip. The phone number is derived from this RSA key. Both RSA key and triple DES session key are managed inside the secure chip. All voice encryption and ADPCM compression are performed within the secure chip. No other cryptophone does this. They use the CPU of the mobile phone for cryptographic tasks. A sophisticated lab can easily extract the keys from such unprotected chips. This phone was therefore designed in hardware and software from scratch for it's main function to provide absolute confidential phone conversations by using a specialty secure chip that is built to prevent and withstand any such extraction attempts.
Any logged past internet traffic is worthless data and can not be played back a second time, even if one or both of the phones are in possession with the attacker. A two stage RSA encapsulated session key creation, exchange and assembly method assures this. Furthermore, the RSA modulus is not in plain; not due security reasons, but to assure good randomness while deriving the phone number and also the UDP socket port number from the RSA key.
Every WiFi Phone, after switching on and connecting to a Wi-Fi network, registers itself with the server at www.WiFi-Tele.com. The server stores the RSA public key and current IP address and thus functions as a dynamic DNS service provider.
After initiating a call, a direct UDP link is established between phones to exchange encrypted voice data.
Outgoing calls can be initiated from anywhere in the world just by knowing the other phone's number. To receive calls however, the internet modem/router NAT has to be setup for port forwarding, to allow a caller to reach the phone behind the firewall on the local area network.Only calls between WiFi Phones of this brand are possible. Regular phones can not be called. This WiFi Crypto Phone establishes confidential P2P calls.
Expenses are currently over the 50K$ mark, not including any form of salary or equipment cost. This is my personal project where i have spent over 2 years. I am looking to get feedback from the many great minds in this community so that i might better the design and perhaps i could inspire anyone to create a better world.