# US 2002/0006197 A1 · Stream-cipher method and apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2002/0006197 A1 - Document ID: US20020006197A1 - Status: Published application - Kind: A1 - Application number: 09/851,870 - Filed: 2001-05-09 - Published: 2002-01-17 - Earliest claimed: 2000-05-09 - Assignees: Verizon Laboratories Inc.; Genuity Inc. - Inventors: Christopher Paul Carroll; Muxiang Zhang; Agnes Chan - Web page: https://patentgrep.com/patent/US20020006197A1 ## CPC - H04L 9/0662: {with particular pseudorandom sequence generator} - H04L 2209/12: Details relating to cryptographic hardware or logic circuitry - H04L 2209/24: Key scheduling, i.e. generating round keys or sub-keys for block encryption - H04L 2209/80: Wireless - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Methods and systems are provided for processing information. In one embodiment, there is provided a method, providing a frame key based on a master key and a frame number of a frame of information to a keystream generator as an initial fill for one or more registers of the keystream generator such that the initial fill establishes a state for the one or more registers of the keystream generator; and generating, at the keystream generator, a keystream sequence based on the state established by the initial fill, wherein the keystream sequence includes a modulo-2 sum of a lagged-Fibonacci sequence and a pseudo-random sequence produced by a filter generator ## Claims ### Claim 1 A method for processing information comprising the steps of: providing a frame key based on a master key and a frame number of a frame of information to a keystream generator as an initial fill for one or more registers of the keystream generator such that the initial fill establishes a state for the one or more registers of the keystream generator; and generating, at the keystream generator, a keystream sequence based on the state established by the initial fill, wherein the keystream sequence includes a modulo-2 sum of a lagged-Fibonacci sequence and a pseudo-random sequence produced by a filter generator. ### Claim 2 (depends on 1) The method of claim 1, further comprising the step of: creating a second frame key based the master key and a second frame number such that the second frame key represents a second frame of information. ### Claim 3 (depends on 1) The method of claim 1, wherein said providing further comprises the step of: initializing the one or more registers of the keystream generator based on the frame key. ### Claim 4 (depends on 1) The method of claim 1, wherein said generating further comprises the step of: shifting one or more bits of a first word corresponding to one of a plurality of registers of the keystream generator; and shifting one or more bits of a second word corresponding to a second of the plurality of registers. ### Claim 5 (depends on 4) The method of claim 4, further comprising the step of: combining the shifted first word with the shifted second word based on exclusive OR logic. ### Claim 6 (depends on 3) The method of claim 3, wherein said initializing further comprises the step of: initializing a first linear feedback shift register of the filter generator with the frame key. ### Claim 7 (depends on 6) The method of claim 6, further comprising the step of: defining the first linear feedback generator of the filter generator as producing the pseudo-random sequence that satisfies the following equation: Sn=Sn−2⊕Sn−3<<31⊕Sn−4>>1, n≧4, wherein <> corresponds to a zero-fill right shift operation, ⊕ denotes XOR logic, and n is the number of stages in the first linear feedback shift register. ### Claim 8 (depends on 1) The method of claim 1, wherein said generating further comprises the step of: producing the lagged-Fibonacci sequence using a lagged-Fibonacci generator. ### Claim 9 (depends on 8) The method of claim 8, further comprising the step of: initializing a second linear feedback shift register of the lagged-Fibonacci generator with the frame key. ### Claim 10 (depends on 8) The method of claim 8, further comprising the step of: defining the lagged-Fibonacci sequence as satisfying the following equation: Ln=Ln−5+Ln−17 mod 232, wherein n corresponds to the number of stages of in the second linear feedback shift register and is greater than or equal to 17 words of 32-bits, and mod 232 corresponds to modulo-2 addition of a 32 bit word. ### Claim 11 (depends on 8) The method of claim 8, further comprising the step of: rotating an output of the lagged-Fibonacci generator. ### Claim 12 (depends on 1) The method of claim 1, further comprising the step of: producing a bit stream of ciphertext by modulo-2 adding each bit in the keystream sequence produced by the keystream generator with a corresponding bit in a bit stream of plaintext. ### Claim 13 (depends on 1) The method of claim 1, further comprising the step of: producing a bit stream of plaintext by modulo-2 adding each bit in the keystream sequence produced by the keystream generator with a corresponding bit in a bit stream of ciphertext. ### Claim 14 A system for processing information, said system comprising: at least one memory including: code that provides a frame key based on a master key and a frame number of a frame of information to a keystream generator as an initial fill for one or more registers of the keystream generator such that the initial fill establishes a state for the one or more registers of the keystream generator, and code that generates, at the keystream generator, a keystream sequence based on the state established by the initial fill, wherein the keystream sequence includes a modulo-2 sum of a lagged-Fibonacci sequence and a pseudo-random sequence produced by a filter generator; and at least one processor that executes said code. ### Claim 15 (depends on 14) The system of claim 14, further comprising: code that creates a second frame key based the master key and a second frame number such that the second frame key represents a second frame of information to be enciphered. ### Claim 16 (depends on 14) The system of claim 14, wherein said code that provides the frame key further comprises: code that initializes the one or more registers of the keystream generator based on the frame key. ### Claim 17 (depends on 14) The system of claim 14, wherein said code that generates further comprises: code that shifts one or more bits of a first word corresponding to one of a plurality of registers of the keystream generator; and code that shifts one or more bits of a second word corresponding to a second of the plurality of registers. ### Claim 18 (depends on 17) The system of claim 17, further comprising: code that combines the shifted first word with the shifted second word based on exclusive OR logic. ### Claim 19 (depends on 16) The system of claim 16, wherein said code that initializes the one or more registers further comprises: code that initializes a first linear feedback shift register of the filter generator with the frame key. ### Claim 20 (depends on 19) The system of claim 19, further comprising: code that defines the first linear feedback generator of the filter generator as producing the pseudo-random sequence that satisfies the following equation: Sn=Sn−2⊕Sn−3<<31⊕Sn−4>>1, n≧4, wherein <> corresponds to a zero-fill right shift operation, ⊕ denotes XOR logic, and n is the number of stages in the first linear feedback shift register. ### Claim 21 (depends on 14) The system of claim 14, wherein said code that generates a keystream sequence further comprises: code that produces the lagged-Fibonacci sequence using a lagged-Fibonacci generator. ### Claim 22 (depends on 21) The system of claim 21, further comprising: code that initializes a second linear feedback shift register of the lagged-Fibonacci generator with the frame key. ### Claim 23 (depends on 21) The system of claim 21, further comprising: code that defines the lagged-Fibonacci sequence as satisfying the following equation: Ln=Ln−17 mod 232, wherein n corresponds to the number of stages of in the second linear feedback shift register and is greater than or equal to 17 words of 32-bits, and mod 232 corresponds to modulo-2 addition of a 32 bit word. ### Claim 24 (depends on 21) The system of claim 21, further comprising: code that rotates an output of the lagged-Fibonacci generator. ### Claim 25 (depends on 14) The system of claim 14, further comprising: code that produces a bit stream of ciphertext by modulo-2 adding each bit in the keystream sequence produced by the keystream generator with a corresponding bit in a bit stream of plaintext. ### Claim 26 (depends on 14) The system of claim 14, further comprising: code that produces a bit stream of plaintext by modulo-2 adding each bit in the keystream sequence produced by the keystream generator with a corresponding bit in a bit stream of ciphertext. ### Claim 27 A computer program product, the computer program product comprising code, said code comprising: code that provides a frame key based on a master key and a frame number of a frame of information to a keystream generator as an initial fill for one or more registers of the keystream generator such that the initial fill establishes a state for the one or more registers of the keystream generator; and code that generates, at the keystream generator, a keystream sequence based on the state established by the initial fill, wherein the keystream sequence includes a modulo-2 sum of a lagged-Fibonacci sequence and a pseudo-random sequence produced by a filter generator. ### Claim 28 (depends on 27) The computer program product of claim 27, said code further comprising: code that produces a bit stream of ciphertext by modulo-2 adding each bit in the keystream sequence produced by the keystream generator with a corresponding bit in a bit stream of plaintext. ### Claim 29 (depends on 27) The computer program product of claim 27, said code further comprising: code that produces a bit stream of plaintext by modulo-2 adding each bit in the keystream sequence produced by the keystream generator with a corresponding bit in a bit stream of ciphertext. ### Claim 30 A hand held device for communicating information, said hand held device comprising: at least one memory including: code that provides a frame key based on a master key and a frame number of a frame of information to a keystream generator as an initial fill for one or more registers of the keystream generator such that the initial fill establishes a state for the one or more registers of the keystream generator, and code that generates, at the keystream generator, a keystream sequence based on the state established by the initial fill, wherein the keystream sequence includes a modulo-2 sum of a lagged-Fibonacci sequence and a pseudo-random sequence produced by a filter generator; at least one processor that executes said code. ### Claim 31 (depends on 30) The hand held device of claim 30, further comprising: code that receives code and information from a base station. ### Claim 32 (depends on 31) The hand held device of claim 31, further comprising: code that configures the keystream generator based on the received code and information. ### Claim 33 (depends on 30) The hand held device of claim 30, further comprising: code that receives one or more keys from a base station such that the one or more keys initialize one or more registers of the keystream generator.