SECURE HAND-HELD RADIO WITH RC4 ENCRYPTION
The aim of this paper is to demonstrate and propose the development of a secure two-way communication system. This works through frequency modulation (FM) of the voice, and RC4 encryption for security. This is useful in providing a secure and unbilled voice service within a small radius.
To demonstrate the working of our system, three devices are made such that each has a transmitter and receiver circuit on the same board, but using different channels of unlicensed frequency. Two of the devices have an encryption or decryption system coupled between the voice section and the radio frequency section. The third device acts as an intruder and is used to determine whether or not the cryptosystems are functional in preventing intrusion. It has two receiver circuits tuned to the two frequencies used but without a cryptosystem coupled to either.
Our experiments revealed that, without the cryptosystems turned on, the third device receives signals from either of the other two devices. However, when encryption is incorporated, it receives gibberish, confirming that the channels have been made secure. The experiments were qualitative rather than quantitative in nature.
A high transmit power in each of the transmitter circuits is desired to achieve a high signal-to-noise ratio, and also enable the signal to be propagated within an area of a fairly large radius. This enables two users to cancel unnecessary costs that may be incurred for communication within that locality. The developed prototype would be helpful in applications such as police and intra-office communication.