Avtor/Urednik		Korošin, Borut; Kodek, Dušan; Trobec, Roman
Naslov		Izvedba analognega asinhronskega govornega skremblerja
Prevedeni naslov		Implementation of analog asynchronous speech scrambler
Tip		članek
Vir		Elektroteh Vestn
Vol. in št.		Letnik 64, št. 5
Leto izdaje		1997
Obseg		str. 253-63
Jezik		slo
Abstrakt		Security of speech communications is of crucial importance in today's telecommunications. Many different methods have been used to ensure the privacy of speech communications. They can be broadly divided into digital and analog methods. Digital methods transform speech signal into a low-rate stream of digits which is then scrambled by some encryption algorithms and transmitted in digital form. Analog methods work on the original speech signal which is scrambled into a different analog signal. Both digital and analog methods are today usually implemented digitally with digital signal processors. Analog methods are significantly less safe than digital ones. They are, however, more tolerant to transmission errors and can be used on low quality communications channels where digital methods no longer work. Some of the analog methods completely eliminate the need for frame synchronizatio which makes them especially attractive. They are also less expensive to implement than the digital methods and easy to add to an existing communications equipment. This explains the existing interest in analog scramblers and in the new methods for their design. The paper describes an implementation of ananalog asynchronous (i.e. no synchronization) speech scrambler. The method is based on the ideas given by French (4). Portnoff (5), and Lee and Chou (6). Encryptoion is performed in the domain of Fourier transform by permutation of N frequency bands; the encrypted spectrum is then transformed back into the timedomain. This gives a scrambled analog signal with spectrmthat is similar to the original speech spectrum. Unscrambling is done by performing the encryptionoperations in the reverse order. (Abstract truncated at 2000 characters.)
Deskriptorji		COMPUTER SECURITY USER-COMPUTER INTERFACE SPEECH TELECOMMUNICATIONS