1. Technical Field
This invention relates in general to communications and, more particularly, to spread spectrum communications and data encryption.
2. Description of the Related Art
Spread spectrum communication devices have been used in military and commercial devices for many years. These devices use noise-like waves to spread (cover) the information bits so that transmission bandwidth is much wider than that required for simple point-to-point communication. DS-CDMA (Direct Spreading Code Division Multiple Access) is a form of spread spectrum which uses a conventional communication waveform and a pseudo-noise (PN) sequence to transmit information. The PN sequence is commonly generated using a Linear Feedback Shift Register (LFSR).
In addition to its improved capacity and quality, spread spectrum techniques provide secure communications, since the receiver will generate the same PN sequence as the transmitter. While normal spread spectrum devices are very secure relative to other communication devices, it is possible to determine the polynomial being used to generate the pseudo-noise sequence, since there are a finite number of polynomials for a given sequence length. While third-party deciphering the pseudo-noise sequence may require significant computing power, it is possible that such resources may be available to decipher highly confidential communications.
Accordingly, a need has arisen for a method and apparatus for generating a PN sequence which is difficult to decipher.