Title:
A METHOD OF SCRAMBLING A SIGNAL
Document Type and Number:
WIPO Patent Application WO2001054341
Kind Code:
A3
Abstract:
A method of scrambling a compressed audio and/or picture signal to provide a scrambled signal for distribution, the information content being recoverable from the scrambled signal using descrambling means (10) under the control of authorised recipients of the scrambled signal, is described. The method consists of or includes: a) encoding the information content using a wavelet filterbank having a tree structure; b) distributing the scrambled signal to authorised recipients; and c) decoding the information content using the corresponding inverse wavelet filterbank. The wavelet filter used, the wavelet filterbank tree structure, the number of decomposition stages in the tree structure and/or the time for which a given filter or tree structure or number of decomposition stages is used can be changed in an apparently random fashion to improve security whilst keeping the scrambled signal recognisable. Progressively increasing distortion with time is also described.
Inventors:
KUDUMAKIS PANOS (GB)
Application Number:
PCT/GB2001/000207
Publication Date:
March 14, 2002
Filing Date:
January 22, 2001
Export Citation:
Assignee:
CENTRAL RESEARCH LAB LTD (GB)
KUDUMAKIS PANOS (GB)
KUDUMAKIS PANOS (GB)
International Classes:
H04N5/92; G10L19/00; G10L19/02; G10L25/51; H04K1/00; H04N7/167; H04N21/2347; H04N21/4405; (IPC1-7): H04N7/167
Other References:
XIAOBO L ET AL: "Image compression and encryption using tree structures", PATTERN RECOGNITION LETTERS, NORTH-HOLLAND PUBL. AMSTERDAM, NL, vol. 18, no. 11-13, 1 November 1997 (1997-11-01), pages 1253 - 1259, XP004117926, ISSN: 0167-8655
KUDUMAKIS P E ; SANDLER M B: "On the compression obtainable with four-tap wavelets", IEEE SIGNAL PROCESS. LETT., vol. 3, no. 8, August 1996 (1996-08-01), (USA), pages 231 - 233, XP002174980, ISSN: 1070-9908
VORWERK L ; ENGEL T ; MEINEL C: "Proposal for a combination of compression and encryption", PROC. SPIE, 2000, vol. 4067, pt.1-3, 23 June 2000 (2000-06-23), USA, pages 694 - 702, XP001019782, ISBN: 0277-786X
JOHNSTON C: "Wavelets defined over finite fields and the discrete wavelet transform", PROC. SPIE, 1995, vol. 2491, pt.2, 21 April 1995 (1995-04-21), USA, pages 915 - 922, XP001019791, ISSN: 0277-786X
KUDUMAKIS P E ; SANDLER M B: "On the compression obtainable with four-tap wavelets", IEEE SIGNAL PROCESS. LETT., vol. 3, no. 8, August 1996 (1996-08-01), (USA), pages 231 - 233, XP002174980, ISSN: 1070-9908
VORWERK L ; ENGEL T ; MEINEL C: "Proposal for a combination of compression and encryption", PROC. SPIE, 2000, vol. 4067, pt.1-3, 23 June 2000 (2000-06-23), USA, pages 694 - 702, XP001019782, ISBN: 0277-786X
JOHNSTON C: "Wavelets defined over finite fields and the discrete wavelet transform", PROC. SPIE, 1995, vol. 2491, pt.2, 21 April 1995 (1995-04-21), USA, pages 915 - 922, XP001019791, ISSN: 0277-786X
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