Traitor tracing

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Traitor tracing schemes help trace the source of leaks when secret or proprietary data is sold to many customers. In a traitor tracing scheme, each customer is given a different personal decryption key. (Traitor tracing schemes are often combined with conditional access systems so that, once the traitor tracing algorithm identifies a personal decryption key associated with the leak, the content distributor can revoke that personal decryption key, allowing honest customers to continue to watch pay television while the traitor and all the unauthorized users using the traitor's personal decryption key are cut off.)

Traitor tracing schemes are used in pay television to discourage pirate decryption – to discourage legitimate subscribers from giving away decryption keys.^{[1][2][3][4][5]} Traitor tracing schemes are ineffective if the traitor rebroadcasts the entire (decrypted) original content. There are other kinds of schemes that discourages pirate rebroadcast – i.e., discourages legitimate subscribers from giving away decrypted original content. These other schemes use tamper-resistant digital watermarking to generate different versions of the original content. Traitor tracing key assignment schemes can be translated into such digital watermarking schemes.^[6][7][8]

Traitor tracing is a copyright infringement detection system which works by tracing the source of leaked files rather than by direct copy protection. The method is that the distributor adds a unique salt to each copy given out. When a copy of it is leaked to the public, the distributor can check the value on it and trace it back to the "leak".