On Tuesdays the USPTO issues new patents. Today's Spotlight Patents address conditional access systems used in video distribution. Assigned to TiVo, the first patent concerns conditional access techniques including those that prevent replay attacks. Assigned to SmarDTV SA, the second patent concerns techniques for selective multimedia encryption.
7,590,240, "Conditional access system and method prevention of replay attacks," assigned to TiVo Inc.
Abstract
In a conditional access system, a headend transmits content to one or more receivers in encrypted transport streams. The system provides a multi-layer security architecture, rendering the system resistant to key replay attacks; if one layer is circumvented, subsequent layers remain intact. A first layer prevents unencrypted keys from being recorded by shielding the unencrypted keys from users and encrypting the path from the receiver's conditional access module to the transport decryption module; a second layer prevents a key recorded on one receiver from being played back to the transport decryption module on a second receiver; a third layer prevents a user from decrypting transport streams without the encryption module by encrypting the stream a second time prior to being passed through any user-accessible memory or processor. Events tables are transmitted with the transport stream, either unencrypted for immediate use or encrypted, to prevent unauthorized use.
7,590,242, "Selective multimedia data encryption," assigned to SmarDTV SA (CH).
Abstract
A conditional access system for multimedia data is disclosed that offers acceptable security at drastically reduced requirements on hardware performance. A selectively encrypted transport stream is formed from a clear transport stream by detecting particular data packets within the clear transport stream, removing and encrypting the particular data packets with an event encryption key, and inserting the encrypted data packets into the remaining clear transport stream at insertion positions corresponding to the original positions of the particular data packets in the clear transport stream. For specific embodiments that include decryption circuitry inside a user smart card, the level of security of such system is even higher than that of conventional ones.
Abstract
In a conditional access system, a headend transmits content to one or more receivers in encrypted transport streams. The system provides a multi-layer security architecture, rendering the system resistant to key replay attacks; if one layer is circumvented, subsequent layers remain intact. A first layer prevents unencrypted keys from being recorded by shielding the unencrypted keys from users and encrypting the path from the receiver's conditional access module to the transport decryption module; a second layer prevents a key recorded on one receiver from being played back to the transport decryption module on a second receiver; a third layer prevents a user from decrypting transport streams without the encryption module by encrypting the stream a second time prior to being passed through any user-accessible memory or processor. Events tables are transmitted with the transport stream, either unencrypted for immediate use or encrypted, to prevent unauthorized use.
7,590,242, "Selective multimedia data encryption," assigned to SmarDTV SA (CH).
Abstract
A conditional access system for multimedia data is disclosed that offers acceptable security at drastically reduced requirements on hardware performance. A selectively encrypted transport stream is formed from a clear transport stream by detecting particular data packets within the clear transport stream, removing and encrypting the particular data packets with an event encryption key, and inserting the encrypted data packets into the remaining clear transport stream at insertion positions corresponding to the original positions of the particular data packets in the clear transport stream. For specific embodiments that include decryption circuitry inside a user smart card, the level of security of such system is even higher than that of conventional ones.
