# US 2023/0412397 A1 · Transitioning To and From Crypto-Agile Hybrid Public Key Infrastructures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0412397 A1 - Document ID: US20230412397A1 - Status: Published application - Kind: A1 - Application number: 18/336,487 - Filed: 2023-06-16 - Published: 2023-12-21 - Earliest claimed: 2022-06-16 - Assignees: ISARA Corporation - Applicants: ISARA Corporation - Inventors: Rene Gollent; Atsushi Yamada; Jiayuan Sui - Web page: https://patentgrep.com/patent/US20230412397A1 ## CPC - H04L 9/3265: {using certificate chains, trees or paths; Hierarchical trust model} - H04L 9/006: {involving public key infrastructure [PKI] trust models (network architecture or network communication protocol for supporting authentication of entities using certificates in a packet data network H04L63/0823)} - H04L 9/007: {involving hierarchical structures} - H04L 9/0891: {Revocation or update of secret information, e.g. encryption key update or rekeying} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract In a general aspect, digital certificates are generated. In some aspects, a method includes accessing a primary root certificate of a root certificate authority of a PKI system. The primary root certificate includes a first public key based on a first cryptosystem and a first signature generated with a private key that corresponds to the first public key. A secondary crypto-agile root certificate is generated. The secondary crypto-agile root certificate includes the first public key of the root certificate authority, a second public key of the root certificate authority that is based on a second cryptosystem, a second signature of the root certificate authority that is created with a second private key that corresponds to the second public key, and a third signature of the root certificate authority that is generated with the first private key. The secondary crypto-agile root certificate is propagated to subordinate entities in the PKI system. ## Claims ### Claim 1 A method comprising: accessing a primary root certificate of a root certificate authority of a PKI system, the primary root certificate comprising a first public key based on a first cryptosystem and a first signature generated with a private key that corresponds to the first public key; generating a secondary crypto-agile root certificate of the root certificate authority, the secondary crypto-agile root certificate comprising: the first public key of the root certificate authority; a second public key of the root certificate authority based on a second cryptosystem; a second signature of the root certificate authority generated with a second private key that corresponds to the second public key; and a third signature of the root certificate authority generated with the first private key; and propagating the secondary crypto-agile root certificate to at least one subordinate entity in the PKI system, wherein propagating the secondary crypto-agile root certificate causes the secondary crypto-agile root certificate to be inserted in a certificate chain between the primary root certificate and a certificate of an intermediate certificate authority. ### Claim 2 (depends on 1) The method of claim 1, wherein propagating the secondary crypto-agile root certificate comprises notifying the intermediate certificate authority that the secondary crypto-agile root certificate is available. ### Claim 3 (depends on 2) The method of claim 2, wherein the propagating further comprises: responsive to a request from the intermediate certificate authority, generating a secondary crypto-agile certificate of the intermediate certificate authority, the secondary crypto-agile certificate of the intermediate certificate authority comprising: a first public key of the intermediate certificate authority based on the first cryptosystem; a second public key of the intermediate certificate authority based on the second cryptosystem; a first signature generated with the first private key of the root certificate authority; and a second signature generated with the second private key of the root certificate authority; and sending the secondary crypto-agile certificate of the intermediate certificate authority to the intermediate certificate authority. ### Claim 4 (depends on 2) The method of claim 2, wherein the intermediate certificate authority is a first-level intermediate certificate authority, and propagating the secondary crypto-agile root certificate comprises propagating the secondary crypto-agile root certificate to a plurality of intermediate certificate authorities and a plurality of end entities. ### Claim 5 (depends on 4) The method of claim 4, wherein the plurality of certificate authorities comprises the first-level intermediate certificate authority and a second-level intermediate certificate authority. ### Claim 6 (depends on 1) The method of claim 1, wherein propagating the secondary crypto-agile root certificate comprises propagating the secondary crypto-agile root certificate to a plurality of first-level intermediate certificate authorities. ### Claim 7 (depends on 6) The method of claim 6, wherein each of the plurality of first-level intermediate certificate authorities propagates the secondary crypto-agile root certificate to one or more second-level intermediate certificate authorities. ### Claim 8 (depends on 1) The method of claim 1, further comprising, after propagating the secondary crypto-agile root certificate: generating a new root certificate of the certificate authority, the new root certificate comprising: the second public key of the root certificate authority; and a fourth signature of the root certificate authority generated with the second private key; and propagating the new root certificate to the at least one subordinate entity, wherein propagating the new root certificate causes the primary root certificate and the secondary crypto-agile certificate to be replaced by the new root certificate in the certificate chain. ### Claim 9 (depends on 8) The method of claim 8, wherein the new root certificate is propagated to upgrade the PKI system from the first cryptosystem to the second cryptosystem, and the new root certificate is formatted according to a digital certificate standard. ### Claim 10 A computer system comprising: one or more processors; and memory storing instructions that are operable when executed by the one or more processors to perform operations comprising: accessing a primary root certificate of a root certificate authority of a PKI system, the primary root certificate comprising a first public key based on a first cryptosystem and a first signature generated with a private key that corresponds to the first public key; generating a secondary crypto-agile root certificate of the root certificate authority, the secondary crypto-agile root certificate comprising: the first public key of the root certificate authority; a second public key of the root certificate authority based on a second cryptosystem; a second signature of the root certificate authority generated with a second private key that corresponds to the second public key; and a third signature of the root certificate authority generated with the first private key; and propagating the secondary crypto-agile root certificate to at least one subordinate entity in the PKI system, wherein propagating the secondary crypto-agile root certificate causes the secondary crypto-agile root certificate to be inserted in a certificate chain between the primary root certificate and a certificate of an intermediate certificate authority. ### Claim 11 (depends on 10) The computer system of claim 10, wherein propagating the secondary crypto-agile root certificate comprises notifying the intermediate certificate authority that the secondary crypto-agile root certificate is available. ### Claim 12 (depends on 11) The computer system of claim 11, wherein the propagating further comprises: responsive to a request from the intermediate certificate authority, generating a secondary crypto-agile certificate of the intermediate certificate authority, the secondary crypto-agile certificate of the intermediate certificate authority comprising: a first public key of the intermediate certificate authority based on the first cryptosystem; a second public key of the intermediate certificate authority based on the second cryptosystem; a first signature generated with the first private key of the root certificate authority; and a second signature generated with the second private key of the root certificate authority; and sending the secondary crypto-agile certificate of the intermediate certificate authority to the intermediate certificate authority. ### Claim 13 (depends on 11) The computer system of claim 11, wherein the intermediate certificate authority is a first-level intermediate certificate authority, and propagating the secondary crypto-agile root certificate comprises propagating the secondary crypto-agile root certificate to a plurality of intermediate certificate authorities and a plurality of end entities. ### Claim 14 (depends on 13) The computer system of claim 13, wherein the plurality of certificate authorities comprises the first-level intermediate certificate authority and a second-level intermediate certificate authority. ### Claim 15 (depends on 10) The computer system of claim 10, wherein propagating the secondary crypto-agile root certificate comprises propagating the secondary crypto-agile root certificate to a plurality of first-level intermediate certificate authorities. ### Claim 16 (depends on 10) The computer system of claim 10, the operations further comprising, after propagating the secondary crypto-agile root certificate: generating a new root certificate of the certificate authority, the new root certificate comprising: the second public key of the root certificate authority; and a fourth signature of the root certificate authority generated with the second private key; and propagating the new root certificate to the at least one subordinate entity, wherein propagating the new root certificate causes the primary root certificate and the secondary crypto-agile certificate to be replaced by the new root certificate in the certificate chain. ### Claim 17 A non-transitory computer-readable medium comprising instructions that, when executed by data processing apparatus of a computer system, perform operations comprising: accessing a primary root certificate of a root certificate authority of a PKI system, the primary root certificate comprising a first public key based on a first cryptosystem and a first signature generated with a private key that corresponds to the first public key; generating a secondary crypto-agile root certificate of the root certificate authority, the secondary crypto-agile root certificate comprising: the first public key of the root certificate authority; a second public key of the root certificate authority based on a second cryptosystem; a second signature of the root certificate authority generated with a second private key that corresponds to the second public key; and a third signature of the root certificate authority generated with the first private key; and propagating the secondary crypto-agile root certificate to at least one subordinate entity in the PKI system, wherein propagating the secondary crypto-agile root certificate causes the secondary crypto-agile root certificate to be inserted in a certificate chain between the primary root certificate and a certificate of an intermediate certificate authority. ### Claim 18 (depends on 17) The non-transitory computer readable medium of claim 17, wherein propagating the secondary crypto-agile root certificate comprises notifying the intermediate certificate authority that the secondary crypto-agile root certificate is available. ### Claim 19 (depends on 18) The non-transitory computer readable medium of claim 18, wherein the propagating further comprises: responsive to a request from the intermediate certificate authority, generating a secondary crypto-agile certificate of the intermediate certificate authority, the secondary crypto-agile certificate of the intermediate certificate authority comprising: a first public key of the intermediate certificate authority based on the first cryptosystem; a second public key of the intermediate certificate authority based on the second cryptosystem; a first signature generated with the first private key of the root certificate authority; and a second signature generated with the second private key of the root certificate authority; and sending the secondary crypto-agile certificate of the intermediate certificate authority to the intermediate certificate authority. ### Claim 20 (depends on 18) The non-transitory computer readable medium of claim 18, wherein the intermediate certificate authority is a first-level intermediate certificate authority, and propagating the secondary crypto-agile root certificate comprises propagating the secondary crypto-agile root certificate to a plurality of intermediate certificate authorities and a plurality of end entities.