# US 2020/0404392 A1 · Secure provisioning, by a client device, cryptographic keys for exploiting services provided by an operator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0404392 A1 - Document ID: US20200404392A1 - Status: Published application - Kind: A1 - Application number: 17/012,440 - Filed: 2020-09-04 - Published: 2020-12-24 - Earliest claimed: 2015-12-23 - Assignees: Nagravision S.A. - Applicants: Nagravision S.A. - Inventors: Yann BIEBER; André NICOULIN - Web page: https://patentgrep.com/patent/US20200404392A1 ## CPC - H04N 21/835: Generation of protective data, e.g. certificates {(protecting software against unauthorised usage in a vending or licensing environment G06F21/10)} - H04L 9/0819: {Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) (network architectures or network communication protocols for key distribution in a packet data network H04L63/062)} - H04L 9/0822: {using key encryption key} - H04L 9/0825: {using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates} - H04L 9/083: {involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]} - H04L 9/088: {Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms (network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068)} - H04L 9/14: using a plurality of keys or algorithms - H04L 9/16: the keys or algorithms being changed during operation - H04N 7/1675: {Providing digital key or authorisation information for generation or regeneration of the scrambling sequence (pseudo-random number generators in general G06F7/58)} - H04N 21/4405: involving video stream decryption - H04N 21/63345: {by transmitting keys (key distribution for secret or secure communication H04L9/08; network support of key management H04L63/06)} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method for securely receiving a multimedia content by a client device operated by one or more operator(s) involving a dedicated provisioning server of a security provider managing symmetric secrets used by the client devices and operators license servers. The provisioning server provides to the client device one or more generations of operator specific unique device secrets, which are then exploited by the various operators' license servers to deliver licenses such that authorized client devices can consume protected multimedia contents. ## Claims ### Claim 1 A method of descrambling a scrambled service, comprising: transmitting, by a client device, a first challenge to an operator server, the first challenge including at least a certificate corresponding to the client device; receiving, by the client device in response to the first challenge, a license from the operator server, the license including at least a service key encrypted with a unique device-derived key; determining, by the client device, the unique device-derived key by applying a predetermined algorithm on a global operator seed and unique device key corresponding to the client device; decrypting, by the client device, the service key with the calculated unique device-derived key; and receiving and descrambling, by the client device, the scrambled service using the service key. ### Claim 2 (depends on 1) The method according to claim 1, further comprising: prior to transmitting the first challenge, downloading, by the client device from the operator server, a global operator vault that stores the global operator seed; transmitting a second challenge, by the client device to the operator server, the second challenge including at least a unique identified of the client device and an identifier of the operator server; and receiving, by the client device in response to the second challenge, the certificate corresponding to the client. ### Claim 3 (depends on 2) The method according to claim 2, further comprising extracting, by the client device, the global operator seed from the global vault. ### Claim 4 (depends on 3) The method according to claim 3, wherein to extract the global operator seed from the global operator vault, the method further comprises decrypting the global operator vault with a global operator vault key received from the operator server by the client device with the certificate corresponding to the client device. ### Claim 5 (depends on 2) The method according to claim 2, wherein the global operator vault is stored in non-volatile memory in the client device. ### Claim 6 (depends on 2) The method according to claim 2, wherein the global operator value stores a plurality of global operator seeds corresponding to a plurality of cryptographic generations. ### Claim 7 (depends on 6) The method according to claim 6, further comprising changing a cryptographic generation if a current global operator seed is compromised or periodically. ### Claim 8 (depends on 1) The method according to claim 1, wherein the service key includes a content package key encrypted with the unique device-derived key, and a content key encrypted with the content package key. ### Claim 9 (depends on 8) The method according to claim 8, further comprising: decrypting, by the client device, the content package key with the unique device-derived key; and decrypting, by the client device, the content key with the content package key after the content package key is decrypted. ### Claim 10 A client device that descrambles a scrambled service, comprising: circuitry configured to transmit a first challenge to an operator server, the first challenge including at least a certificate corresponding to the device; receive, in response to the first challenge, a license from the operator server, the license including at least a service key encrypted with a unique device-derived key; determine the unique device-derived key by applying a predetermined algorithm on a global operator seed and unique device key corresponding to the client device; decrypt the service key with the calculated unique device-derived key; and receive and descramble the scrambled service using the service key. ### Claim 11 A method of descrambling a scrambled service, comprising: receiving, by an operator server, a first challenge from a client device, the challenge including at least an identifier of the client device and an identifier of the operator server; determining entitlement of the client device to descramble the scrambled service; when the client device is entitled to descramble the scrambled service, retrieving, by the operator server, determining, by the operator server, a device-derived key by applying a predetermined algorithm to a unique device key corresponding to the client device and a global operator seed corresponding to the operator server; forming, by the operator server, a unique cryptogram by encrypting the device-derived key with the global operator seed; transmitting, from the operator server to the client device, a certificate corresponding to the client device, the certificate including the unique cryptogram; receiving, by the operator server, a second challenge from the client device, the second challenge including at least a certificate corresponding to the client device; and providing, from the operator server to the client device in response to the second challenge, a license from the operator server, the license including at least a service key encrypted with the device-derived key, wherein the client device uses the service key in the license to descramble the scrambled service. ### Claim 12 (depends on 11) The method according to claim 11, further comprising: providing, from the operator server to the client device, a global operator vault including the global operator seed. ### Claim 13 (depends on 12) The method according to claim 12, further comprising: providing, from the operator server to the client device, a plurality of unique cryptograms corresponding to a plurality of encryption generations, wherein the global operator vault includes a plurality of global operator seeds corresponding to the plurality of encryption generations. ### Claim 14 (depends on 13) The method according to claim 13, further comprising: changing a current encryption generation if a current global operator seed is compromised, or periodically. ### Claim 15 (depends on 12) The method according to claim 12, wherein the global operator vault is encrypted with a global operator vault key. ### Claim 16 (depends on 15) The method according to claim 15, further comprising transmitting, by the operator server, the global operator vault key to the client device at a time when the certificate corresponding to the client device is transmitted. ### Claim 17 (depends on 11) The method according to claim 11, wherein the service key includes a content package key encrypted with the device-derived key, and a content key encrypted with the content package key. ### Claim 18 An operator server, comprising: circuitry configured to receive a first challenge from a client device, the challenge including at least an identifier of the client device and an identifier of the operator server; determine entitlement of the client device to descramble the scrambled service; when the client device is entitled to descramble the scrambled service, determine a device-derived key by applying a predetermined algorithm to a unique device key corresponding to the client device and a global operator seed corresponding to the operator server; form a unique cryptogram by encrypting the device-derived key with the global operator seed; transmit, to the client device, a certificate corresponding to the client device, the certificate including the unique cryptogram; receive a second challenge from the client device, the second challenge including at least a certificate corresponding to the client device; and provide, to the client device in response to the second challenge, a license from the operator server, the license including at least a service key encrypted with the device-derived key, wherein the client device uses the service key in the license to descramble the scrambled service. ### Claim 19 (depends on 18) An operator server according to claim 18, wherein the circuitry is further configured to: provide, to the client device, a plurality of unique cryptograms corresponding to a plurality of encryption generations, wherein the global operator vault includes a plurality of global operator seeds corresponding to the plurality of encryption generations. ### Claim 20 (depends on 19) The operator server according to claim 19, wherein the circuitry is further configured to change a current encryption generation if a current global operator seed is compromised, or periodically.