# US 12,010,247 B2 · Implementation of a butterfly key expansion scheme > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,010,247 B2 - Document ID: US12010247B2 - Status: Granted - Kind: B2 - Application number: 17/607,874 - Filed: 2020-05-14 - Published: 2022-06-16 - Granted: 2024-06-11 - Earliest claimed: 2019-05-14 - Assignees: Volkswagen Aktiengesellschaft - Applicants: Volkswagen Aktiengesellschaft - Inventors: Benedikt Brecht - Web page: https://patentgrep.com/patent/US12010247B2 ## CPC - H04L 9/3263: {involving certificates, e.g. public key certificate [PKC] or attribute certificate [AC]; Public key infrastructure [PKI] arrangements (network architectures or network communication protocols for supporting authentication of entities using certificates in a packet data network H04L63/0823)} - H04L 9/3268: {using certificate validation, registration, distribution or revocation, e.g. certificate revocation list [CRL]} - H04L 9/0869: {involving random numbers or seeds} - H04L 63/0823: {using certificates (cryptographic mechanisms or cryptographic arrangements for entity authentication involving certificates H04L9/3263)} - H04L 9/3066: {involving algebraic varieties, e.g. elliptic or hyper-elliptic curves} - H04L 2209/42: Anonymization, e.g. involving pseudonyms - H04L 2209/84: Vehicles - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Methods, computer programs, and registration authority modules for implementing a butterfly key expansion scheme. The method includes receiving a public caterpillar signing key of a private/public caterpillar signing key pair and a first pseudorandom function from a requesting device; expanding the public caterpillar signing key into public cocoon signing keys using the first pseudorandom function; generating certificate signing requests based on the public cocoon signing keys; sending the certificate signing requests to a certificate authority module; receiving signed pseudonym certificates from the certificate authority module; and encrypting the signed pseudonym certificates to generate response packages. ## Claims ### Claim 1 A method for implementing a butterfly key expansion scheme, the method comprising: a registration authority module, comprised of software running on a processor, the registration authority module receiving a public caterpillar signing key of a private/public caterpillar signing key pair and a first pseudorandom function from a requesting device; the registration authority module expanding the public caterpillar signing key into public cocoon signing keys using the first pseudorandom function; the registration authority module generating certificate signing requests based on the public cocoon signing keys; the registration authority module sending the certificate signing requests to a certificate authority module; the registration authority module receiving unencrypted signed pseudonym certificates from the certificate authority module; and the registration authority module encrypting the unencrypted signed pseudonym certificates to generate response packages for downloading by the requesting device. ### Claim 2 (depends on 1) The method of claim 1, wherein the certificate signing requests are generated by the registration authority by inserting each public cocoon signing key into a corresponding certificate signing request. ### Claim 3 (depends on 1) The method of claim 1, wherein the certificate signing requests are generated by the registration authority by creating a public butterfly signing key from each public cocoon signing key and inserting each public butterfly signing key into a corresponding certificate signing request. ### Claim 4 (depends on 3) The method of claim 3, wherein the public butterfly signing keys are created by the registration authority from the public cocoon signing keys using random numbers. ### Claim 5 (depends on 4) The method of claim 4, further comprising the registration authority including the random numbers in the response packages. ### Claim 6 (depends on 1) The method of claim 1, wherein the unencrypted signed pseudonym certificates are encrypted using the public cocoon signing keys. ### Claim 7 (depends on 1) The method of claim 1, wherein the unencrypted signed pseudonym certificates are encrypted using public cocoon encryption keys. ### Claim 8 (depends on 7) The method of claim 7, wherein the public cocoon encryption keys are derived by expanding a public caterpillar encryption key of a private/public caterpillar encryption key pair using a second pseudorandom function. ### Claim 9 (depends on 8) The method of claim 8, wherein the public caterpillar encryption key and the second pseudorandom function are received by the registration authority module from the requesting device. ### Claim 10 (depends on 7) The method of claim 7, further comprising the registration authority signing the response packages. ### Claim 11 (depends on 1) The method of claim 1, further comprising the registration authority providing the response packages for download by the requesting device. ### Claim 12 (depends on 1) A non-transitory computer readable medium including a computer program comprising instructions, which, when executed by the computer, cause the computer to perform the method of claim 1 for implementing a butterfly key expansion scheme. ### Claim 13 A registration authority module configured to implement a butterfly key expansion scheme, the registration authority module comprising: a first transmission module to receive a public caterpillar signing key of a private/public caterpillar signing key pair and a first pseudorandom function from a requesting device; an expansion module to expand the public caterpillar signing key into public cocoon signing keys using the first pseudorandom function; a generator module to generate certificate signing requests based on the public cocoon signing keys; a second transmission module to send the certificate signing requests to a certificate authority module and to receive unencrypted signed pseudonym certificates from the certificate authority module; and an encryption module to encrypt the unencrypted signed pseudonym certificates to generate response packages for downloading by the requesting device, wherein the registration authority module and its constituent modules are comprised of software running on a processor. ### Claim 14 (depends on 13) A security credential management system comprising: the registration authority module of claim 13 that performs a method for implementing a butterfly key expansion scheme. ### Claim 15 (depends on 13) The registration authority module of claim 13, wherein the certificate signing requests are generated by inserting each public cocoon signing key into a corresponding certificate signing request. ### Claim 16 (depends on 13) The registration authority module of claim 13, wherein the certificate signing requests are generated by creating a public butterfly signing key from each public cocoon signing key and inserting each public butterfly signing key into a corresponding certificate signing request. ### Claim 17 (depends on 16) The registration authority module of claim 16, wherein the public butterfly signing keys are created from the public cocoon signing keys using random numbers. ### Claim 18 (depends on 17) The registration authority module of claim 17, wherein the random numbers are included in the response packages. ### Claim 19 (depends on 13) The registration authority module of claim 13, wherein the unencrypted signed pseudonym certificates are encrypted using the public cocoon signing keys. ### Claim 20 (depends on 13) The registration authority module of claim 13, wherein the unencrypted signed pseudonym certificates are encrypted using public cocoon encryption keys. ### Claim 21 (depends on 20) The registration authority module of claim 20, wherein the public cocoon encryption keys are derived by expanding a public caterpillar encryption key of a private/public caterpillar encryption key pair using a second pseudorandom function. ### Claim 22 (depends on 21) The registration authority module of claim 21, wherein the public caterpillar encryption key and the second pseudorandom function are received by the registration authority module from the requesting device. ### Claim 23 (depends on 20) The registration authority module of claim 20, wherein the response packages are signed. ### Claim 24 (depends on 1) The registration authority module of claim 1, wherein the response packages are provided for download by the requesting device.