Abstract: A key security system provides for the reproduction of secure keys by using distributed key generation data and a distributed encrypted prekey. The system encrypts program key generation data with a program key prekey in accordance with a first encryption algorithm to produce the program key; processes the program key to produce a keystream; and processes an information signal with the keystream to produce a scrambled information signal. The program key prekey is encrypted with a category key in accordance with a second encryption algorithm to produce an encrypted program key prekey. The scrambled information signal, the program key generation data and the encrypted program key prekey are distributed to descramblers.

Abstract: A system for companding digital audio signal samples processes the digital audio signal samples to correct errors induced by the compression and expansion processes. These errors are calculated prior to compressing the samples. Such errors are calculated in accordance with a predetermined compression process and a predetermined expansion process; and the digital audio signal samples are corrected in accordance with such calculations prior to compression. The compression process includes providing a 3-bit gain word for a block of 70 samples. The gain word is computed in accordance with the position of the most significant "1" bit in the sample(s) having the peak magnitude. Each individual sample is processed in accordance with the block gain word to compress the sample by reducing the number of magnitude bits.

Abstract: A system for scrambling a video signal having a plurality of horizontal lines, each of which includes a video information portion and a non-video information portion. The scrambling system includes a memory; means for storing the video information portion of each video signal line in the memory; and means for forming scrambled horizontal lines by retrieving each of a plurality of said stored video information lines in a plurality of segments preceded by a non-video segment and separated by non-video segment(s). The retrieval means include means for varying the respective durations of the retrieved video information segments in individual scrambled horizontal lines in accordance with an encryption keystream; and means for varying the total duration of the non-video segments for individual scrambled horizontal lines in accordance with a predetermined timing pattern. A complementary descrambling system also is disclosed.