# US 2014/0208116 A1 · Communication apparatus, communication system, and computer program product > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0208116 A1 - Document ID: US20140208116A1 - Status: Published application - Kind: A1 - Application number: 14/161,049 - Filed: 2014-01-22 - Published: 2014-07-24 - Earliest claimed: 2013-01-22 - Assignees: Kabushiki Kaisha Toshiba - Applicants: Kabushiki Kaisha Toshiba - Inventors: Yoshimichi Tanizawa; Hideaki Sato; Shinichi Kawamura - Web page: https://patentgrep.com/patent/US20140208116A1 ## CPC - H04L 63/06: {for supporting key management in a packet data network (cryptographic mechanisms or cryptographic arrangements for key management H04L9/08)} - H04L 9/0816: {Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use} - 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 63/04: {for providing a confidential data exchange among entities communicating through data packet networks} - H04L 63/0428: {wherein the data content is protected, e.g. by encrypting or encapsulating the payload} - H04L 63/0435: {wherein the sending and receiving network entities apply symmetric encryption, i.e. same key used for encryption and decryption (cryptographic mechanisms or cryptographic arrangements for symmetric key encryption H04L9/06)} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract According to an embodiment, a communication apparatus includes a sharing processing unit, an extension unit, and a communication unit. The sharing processing unit shares a first cryptographic key with an external apparatus connected via a link, and further generates a second cryptographic key and shares the second cryptographic key with the external apparatus through secret communication using the first cryptographic key. The extension unit generates an extended key by extending a length of the second cryptographic key. The communication unit transmits the extended key to a first application which communicates with a second application to which the external apparatus provides the second cryptographic key. ## Claims ### Claim 1 A communication apparatus, comprising: a sharing processing unit configured to share a first cryptographic key with an external apparatus connected via a link, and further generate a second cryptographic key and share the second cryptographic key with the external apparatus through secret communication using the first cryptographic key; an extension unit configured to generate an extended key by extending a length of the second cryptographic key; and a communication unit configured to transmit the extended key to a first application which communicates with a second application to which the external apparatus provides the second cryptographic key. ### Claim 2 (depends on 1) The apparatus according to claim 1, further comprising a control unit configured to determine an extension method, which is executable in common with the external apparatus, from among at least one of extension methods of the second cryptographic key, wherein the extension unit generates the extended key by extending the length of the second cryptographic key according to the determined extension method. ### Claim 3 (depends on 2) The apparatus according to claim 2, wherein the control unit transmits to the external apparatus extension method data indicating at least one of executable extension methods, receives from the external apparatus the extension method determined by the external apparatus from among the extension methods indicated by the extension method data, and determines the received extension method as the extension method which is executable in common with the external apparatus. ### Claim 4 (depends on 3) The apparatus according to claim 3, wherein the control unit transmits to the external apparatus the extension method data including a priority order of the extension methods, receives from the external apparatus the extension method determined by the external apparatus based on the priority order from among the extension methods indicated by the extension method data, and determines the received extension method as the extension method which is executable in common with the external apparatus. ### Claim 5 (depends on 2) The apparatus according to claim 2, wherein the control unit transmits to the external apparatus identification information identifying the second cryptographic key which starts application of the extension method, and the extension unit starts the application of the determined extension method to the second cryptographic key identified by the identification information. ### Claim 6 (depends on 1) The apparatus according to claim 1, further comprising a control unit configured to determine an extension method of the second cryptographic key based on a throughput of the second cryptographic key requested by the first application and based on a sharing speed of at least one of the first cryptographic key and the second cryptographic key with the external apparatus. ### Claim 7 (depends on 6) The apparatus according to claim 6, wherein, when the requested throughput is changed, the control unit determines the extension method based on the changed throughput and the sharing speed. ### Claim 8 (depends on 6) The apparatus according to claim 6, wherein, when at least one of the sharing speed and condition information indicating a condition of sharing processing of at least one of the first cryptographic key and the second cryptographic key with the external apparatus is changed, the control unit determines the extension method based on the throughput and the sharing speed. ### Claim 9 (depends on 1) The apparatus according to claim 1, wherein the extension unit generates the extended key by replacing data included in the second cryptographic key with conversion data which is determined according to a pattern of the data and which is longer than the data. ### Claim 10 (depends on 1) The apparatus according to claim 1, wherein, using the second cryptographic key as a parameter of cryptograph processing, the extension unit generates, as the extended key, a cryptogram obtained by executing the cryptograph processing on a plaintext. ### Claim 11 (depends on 1) The apparatus according to claim 1, wherein the sharing processing unit shares the second cryptographic key with the external apparatus through the secret communication via one or more other communication apparatuses. ### Claim 12 A communication system including a plurality of communication apparatuses, each of the communication apparatuses comprising: a sharing processing unit configured to share a first cryptographic key with another communication apparatus connected via a link, and further generate a second cryptographic key and share the second cryptographic key with the other communication apparatus through secret communication using the first cryptographic key; an extension unit configured to generate an extended key by extending a length of the second cryptographic key; and a communication unit configured to transmit the extended key to a first application which communicates with a second application to which the other communication apparatus provides the second cryptographic key. ### Claim 13 A computer program product comprising a computer-readable medium containing a computer program that causes a computer to function as: a sharing processing unit configured to share a first cryptographic key with an external apparatus connected via a link, and further generate a second cryptographic key and share the second cryptographic key with the external apparatus through secret communication using the first cryptographic key; an extension unit configured to generate an extended key by extending a length of the second cryptographic key; and a communication unit configured to transmit the extended key to a first application which communicates with a second application to which the external apparatus provides the second cryptographic key.