Abstract
Stream cipher is one of important branch of cryptography that can be implemented by using software and hard ware components .this system is divided into two types :
1.linear stream cipher system .
2. Non- linear stream cipher system .
In this work, we deal with the two type of stream cipher system , the first type doesn’t have top secret degree due to weakness of the linear complexity for the sequence generated from Linear Feedback Shift Register (LFSR) .There are many algorithm ms that are designed by using the process of non- linear combination for more than one linear shift register ,one of these algorithm ,that is called adder algorithm ,is used to generate a key sequence for encryption and deciphering process .The data in form of speech or waveform have been recorded by using computer microphone .these digital speech were encrypted .the encrypted speech has been sent via RS232 standard interface at a bit rate 19.6 kbps to another computer ,and then will be decrypted .
The encrypted data were transmitted through the optical system .a multi mode optical fiber is used as a channel and PIN photo diode is used as an optical detector.
