KEM Certificate Validation With Embedded Proof-of-Possession
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Solution Overview
Problem
Existing methods for validating KEM-based certificates require complex interactions and multiple message exchanges, making it difficult to establish proof-of-possession of the private KEM key.
Innovation Solution
A method that involves generating a ciphertext and a symmetric key using a key encapsulation mechanism, transmitting these to the first entity, and having a second entity verify the possession of the private KEM key by matching values generated using cryptographic functions, thereby shifting the verification process from the certification authority.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex interactions and multiple message exchanges are used for validating KEM-based certificates, then proof-of-possession verification can be achieved, but the validation process becomes complicated and requires extensive communication between entities
Solution Approach 1:
The patent extracts the verification logic from the certification authority and relocates it to the second entity. The certification authority only needs to generate the certificate with embedded validation data, while the actual proof-of-possession verification is performed by the second entity through cryptographic operations on received data, thereby simplifying the overall validation process
Solution Approach 2:
The patent implements preliminary action by embedding validation data (first value) into the certificate during issuance by the certification authority. This pre-prepared validation data enables the second entity to perform verification without requiring complex real-time interactions with the certification authority, thus simplifying the validation process
2Reliability
If multiple message exchanges are used for certificate validation, then verification can be performed, but the number of communication steps increases
Solution Approach 1:
The verification functionality is extracted from the certification authority and assigned to the second entity. This allows the validation process to be completed in a single communication round between the first entity and second entity, eliminating the need for multiple message exchanges with the certification authority and reducing validation time
Solution Approach 2:
The second entity performs self-service verification by independently validating the certificate using cryptographic operations on the embedded first value and generated second value, without requiring additional communication with the certification authority, thus reducing the number of message exchanges
3Reliability
If certificate revocation mechanisms are implemented for failed possession verification, then security is maintained, but the system complexity increases
Solution Approach 1:
The patent implements preliminary action by embedding validation data in the certificate that enables the second entity to verify proof-of-possession independently. This prevents the need for certificate revocation mechanisms because the verification failure can be detected and handled locally without requiring complex revocation procedures, thus reducing system complexity while maintaining security
Data Source
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AI summary
The invention relates to a method for validating a KEM-based certificate (cert), where the certificate (cert) has been issued for a first entity (A) by a certification authority (CA) based on a public KEM key (pk) belonging to the first entity (A) and generated by a key encapsulation mechanism. The method of the invention comprises the following steps: a) generating, by the certification authority (CA), a ciphertext (c) and a symmetric key (k) as well a first value (h(r), t), the ciphertext (c) and the symmetric key (k) being generated from the public KEM key (pk) with an encapsulation procedure (Encaps) of the key encapsulation mechanism and the first value (h(r), t) being generated with a cryptographic function (h, MACk); b) transmitting, by the certification authority (CA), the ciphertext (c) and the certificate (cert) to the first entity (A), where the certificate (cert) includes the public KEM key (pk) and the first value (h(r), t); c) generating, by the first entity (A), a symmetric key (k) from a secret KEM key (sk) and the cipher text (c) with a decapsulation procedure (Decaps) of the key encapsulation mechanism; d) transmitting, by the first entity (A), the certificate (cert) and a second value (r, k) to a second entity (B), the second value (r, k) being the symmetric key (k) generated in step c) or a value (r) generated by using the symmetric key (k); e) generating, by the second entity (B), a third value (u) with the cryptographic function (h, MACk) used for generating the first value (h(r), t), the cryptographic function (h, MACk) processing the second value (r, k), where the certificate (cert) is accepted by the second entity (B) in case that the third value (u) matches the first value (h(r), t) included in the certificate (cert) transmitted in step d).