Method of protecting broadcast data by fingerprinting a common decryption function
First Claim
1. A method of fingerprinting a common function in broadcast systems comprising the steps of(a) determining for each customer a unique function,(b) arranging the functions to be identical on a subset X of inputs, and different (with high probability) on other inputs, and(c) broadcasting only inputs in X in order to enable all customers to compute common outputs, whereby to enable pirate cards to be traced to particular customers by analyzing their computations on arguments which are not necessarily in X.
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Accused Products
Abstract
A well-known technique to discourage piracy of digital objects is to fingerprint the version each customer receives. The invention provides a novel way of fingerprinting the decryption functions given by broadcasters to their customers (usually in the form of smart cards). The main difficulty is to ensure that all the algorithms provided by the broadcaster implement the same decryption function, and yet to make it computationally difficult for a pirate who obtains a large number of such implementations to find even one fundamentally different implementation which is not traceable to a particular customer.
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Citations
21 Claims
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1. A method of fingerprinting a common function in broadcast systems comprising the steps of
(a) determining for each customer a unique function, (b) arranging the functions to be identical on a subset X of inputs, and different (with high probability) on other inputs, and (c) broadcasting only inputs in X in order to enable all customers to compute common outputs, whereby to enable pirate cards to be traced to particular customers by analyzing their computations on arguments which are not necessarily in X.
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8. A method of fingerprinting a common function in broadcast systems comprising the steps of:
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(a) establishing for each customer of a broadcaster a unique function and a unique modification table, (b) broadcasting to each customer a common input, (c) receiving, by each customer, the common input, (d) applying, by each customer, to the common input his unique function and modifying the result with entries from his unique modification table, (e) the results being identical on a subset X of inputs, and different (with high probability) on other inputs, so that (f) pirate functions are traceable to particular customers by analyzing the unique key and modification table used in their computations. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. Apparatus for fingerprinting a common function in broadcast systems comprising:
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(a) a first controller for establishing for each customer of a broadcaster a unique function and a unique modification table, (b) a broadcaster for broadcasting to each customer a common input, (c) a receiver for receiving, by each customer, the common input, (d) a second controller for applying, by each customer, to the common input his unique function and modifying the result with entries from his unique modification table, (c) the results being identical on a subset X of inputs, and different (with high probability) on other inputs, so that (e) pirate functions are traceable to particular customers by analyzing the unique key and modification table used in their computations. - View Dependent Claims (16)
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17. Apparatus for protecting broadcast data by fingerprinting a common decryption function comprising
(a) a controller for determining for each customer a unique function, with the functions arranged to be identical on a subset X of inputs, and different (with high probability) on other inputs, and (b) a broadcaster to broadcast only inputs in X in order to enable all customers to compute common outputs, whereby to enable pirate cards to be traced to particular customers by analyzing their computations on arguments which are not necessarily in X.
Specification