# US 2014/0192984 A1 · Recovery from decryption errors in a sequence of communication packets > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0192984 A1 - Document ID: US20140192984A1 - Status: Published application - Kind: A1 - Application number: 14/055,922 - Filed: 2013-10-17 - Published: 2014-07-10 - Earliest claimed: 2011-02-16 - Assignees: Marvell World Trade Ltd. - Applicants: Marvell World Trade Ltd. - Inventors: DANNY ALEXANDER; AMIT WIX - Web page: https://patentgrep.com/patent/US20140192984A1 ## CPC - H04L 63/0428: {wherein the data content is protected, e.g. by encrypting or encapsulating the payload} - H04K 1/00: Secret communication - H04L 9/12: Transmitting and receiving encryption devices synchronised or initially set up in a particular manner - H04W 12/02: Protecting privacy or anonymity, e.g. protecting personally identifiable information [PII] - H04W 12/037: of the control plane, e.g. signalling traffic - H04W 12/08: Access security - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04K: SECRET COMMUNICATION; JAMMING OF COMMUNICATION - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A method in a receiver includes receiving from a transmitter a sequence of communication packets, which carry data encrypted with an encryption scheme. The encryption scheme depends on a counter value that is incremented independently by each of the transmitter and the receiver. Attempts are made to decrypt the data of a received packet multiple times using different, respective counter values, to produce multiple respective decrypted outputs. A decrypted output in which the data has been decrypted correctly is identified, the counter value is corrected, and the data of the received packet is recovered from the identified decrypted output. ## Claims ### Claim 1 A method for decrypting data in a received transmission, comprising: in a receiver, receiving from a transmitter a sequence of communication packets, which carry data encrypted with an encryption scheme that depends on a counter value that is incremented independently by each of the transmitter and the receiver; attempting to decrypt the data of a received packet multiple times using different, respective counter values, to produce multiple respective decrypted outputs; after the multiple decrypted outputs have been produced, identifying among the multiple decrypted outputs a decrypted output in which the data has been decrypted correctly; and recovering the data of the received packet from the identified decrypted output. ### Claim 2 (depends on 1) The method according to claim 1, comprising correcting the counter value that is incremented by the receiver to match the counter value that is incremented by the transmitter, based on the counter value of the decrypted output in which the data has been decrypted correctly. ### Claim 3 (depends on 1) The method according to claim 1, wherein identifying the decrypted output in which the data has been decrypted correctly comprises verifying a value of a header field in the received packet. ### Claim 4 (depends on 1) The method according to claim 1, wherein attempting to decrypt the data and identifying the decrypted output comprise iteratively incrementing the counter value and re-attempting to decrypt the data using the incremented counter value, until producing the decrypted output in which the data is decrypted correctly. ### Claim 5 (depends on 1) The method according to claim 1, and comprising recovering the counter value from the decrypted output in which the data has been decrypted correctly, and applying the recovered counter value in decryption of one or more subsequent packets in the sequence. ### Claim 6 (depends on 1) The method according to claim 1, wherein receiving the packets comprises receiving a Wideband Code Division Multiple Access (WCDMA) voice call mapped onto High Speed Packet Access (HSPA) packets, and wherein the counter value comprises a Radio Link Control Hyper-Frame Number (RLC HFN). ### Claim 7 (depends on 1) The method according to claim 1, wherein receiving the packets comprises receiving Internet Protocol (IP) packets in accordance with a Long Term Evolution (LTE) specification, and wherein the counter value comprises a Packet Data Convergence Protocol Hyper-Frame Number (PDCP HFN). ### Claim 8 (depends on 1) The method according to claim 1, wherein decryption of the data using the different counter values is attempted only in response to a failure to decrypt the data using the counter value that is incremented by the receiver. ### Claim 9 Apparatus for decrypting encrypted data, comprising: a receiver front end, which is configured to receive from a transmitter a sequence of communication packets, which carry data encrypted with an encryption scheme that depends on a counter value that is incremented by the transmitter; and a decryption unit, which is configured to attempt to decrypt the data of a received packet multiple times using different, respective counter values so as to produce multiple respective decrypted outputs, to identify among the multiple decrypted outputs, after the multiple decrypted outputs have been produced, a decrypted output in which the data has been decrypted correctly, and to recover the data of the received packet from the identified decrypted output. ### Claim 10 (depends on 9) The apparatus according to claim 9, wherein the decryption unit is configured to correct the counter value that is incremented by the apparatus to match the counter value that is incremented by the transmitter, based on the counter value of the decrypted output in which the data has been decrypted correctly. ### Claim 11 (depends on 9) The apparatus according to claim 9, wherein the decryption unit is configured to identify the decrypted output in which the data has been decrypted correctly by verifying a value of a header field in the received packet. ### Claim 12 (depends on 9) The apparatus according to claim 9, wherein the decryption unit is configured to iteratively increment the counter value and re-attempt to decrypt the data using the incremented counter value, until producing the decrypted output in which the data is decrypted correctly. ### Claim 13 (depends on 9) The apparatus according to claim 9, wherein the decryption unit is configured to recover the counter value from the decrypted output in which the data was decrypted correctly, and to apply the recovered counter value in decryption of one or more subsequent packets in the sequence. ### Claim 14 (depends on 9) The apparatus according to claim 9, wherein the receiver front end is configured to receive a Wideband Code Division Multiple Access (WCDMA) voice call mapped onto High Speed Packet Access (HSPA) packets, and wherein the decryption unit is configured to use a Radio Link Control Hyper-Frame Number (RLC HFN) as the counter value. ### Claim 15 (depends on 9) The apparatus according to claim 9, wherein the receiver front end is configured to receive Internet Protocol (IP) packets in accordance with a Long Term Evolution (LTE) specification, and wherein the decryption unit is configured to use a Packet Data Convergence Protocol Hyper-Frame Number (PDCP HFN) as the counter value. ### Claim 16 (depends on 9) The apparatus according to claim 9, wherein the decryption unit is configured to decrypt the data using the different counter values only in response to a failure to decrypt the data using the counter value that is incremented by the apparatus. ### Claim 17 (depends on 9) A mobile communication terminal comprising the apparatus of claim 9. ### Claim 18 (depends on 9) A chipset for processing signals in a mobile communication terminal, comprising the apparatus of claim 9.