Smart Card Privacy-Preserving Certificate Validation via Encrypted Intermediary
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Solution Overview
Problem
Smart cards face challenges in efficiently verifying certificate validity due to limited processing power and memory, lack of an internal clock, and the need to maintain user privacy, with existing solutions either being costly or compromising privacy.
Innovation Solution
A method where a smart card verifies a service provider's certificate through a third-party identity provider without disclosing the service provider's details, using encrypted messages and a certification authority to check the certificate's validity, ensuring privacy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a smart card verifies certificate validity by checking revocation status through a third party, then certificate validation security is improved, but the service provider's privacy information is disclosed
Solution Approach 1:
The patent introduces an intermediary mechanism where the smart card encrypts the service provider's identifier with the certification authority's public key before sending it to the third party. The third party can verify certificate validity through the encrypted identifier without being able to decrypt or learn the actual service provider identity, thus maintaining privacy while enabling security verification
Solution Approach 2:
The patent applies different cryptographic operations to different parts of the data: the service provider identifier is encrypted with the CA's public key for privacy protection, while the certificate itself is verified through standard cryptographic validation. This allows simultaneous achievement of privacy preservation and security verification through differentiated processing
2Reliability
If a smart card performs certificate verification locally, then security and efficiency are improved, but processing power and memory requirements increase beyond card capabilities
Solution Approach 1:
The patent divides the certificate verification process into segments: the smart card performs local validation of the certificate signature and chain of trust, while delegating the revocation status checking to an external third party. This segmentation allows the card to maintain security through local cryptographic verification without being burdened by the computational complexity of full revocation list management
Solution Approach 2:
The third party acts as an intermediary that handles the computationally intensive task of maintaining and checking revocation status. The smart card simply sends the encrypted identifier and receives a validity response, avoiding the need for the card to store or process large revocation lists while still achieving reliable certificate validation
3Reliability
If a smart card checks certificate revocation status, then certificate validity is improved, but the card's lack of internal clock prevents time-based validity checks
Solution Approach 1:
The patent incorporates validity period information into the certificate data structure itself, which is then encrypted and sent to the third party. The third party performs the time-based validation checks using its own clock, and the results are returned to the smart card. This preliminary action by the third party compensates for the card's lack of time-keeping capability
4Device complexity
If certificate validation is delegated to client-middleware on the host, then smart card processing load is reduced, but security is compromised if the middleware is corrupted
Solution Approach 1:
The patent segments the verification process so that critical security functions (certificate signature verification, chain of trust validation) remain on the secure smart card, while non-critical functions (revocation status querying, time validation) are handled by the external third party. This segmentation maintains security by keeping the card's cryptographic operations intact while reducing its processing burden
Solution Approach 2:
The third party serves as a trusted intermediary that the smart card can rely on for revocation checking without needing to trust the host system's middleware. The card communicates directly with the third party using encrypted identifiers, creating a secure verification path that bypasses potentially compromised host-based middleware
Data Source
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AI summary
The present invention concerns a secure method for a card to verify the validity of a second party certificate through a third party whereas the certificate's owner remains unknown to the third party. For that, the invention proposes a method wherein the card transmits to the third party two elements: - the identifier of the Certification Authority, denoted by CAref, an encrypted message ENC(SN)[PKEncCA], where PKEncCA is a public encryption key of the certification authority CA and SN is an anonymous identifier of the second party. Next, the third party transmits a request status revocation of the certificate including the data (CAref, ENC(SN)[PKEncCA]) to the certification authority corresponding to CAref. Next, the corresponding certification authority decrypts the value ENC(SN)[PKEncCA] and next retrieves the anonymous identifier. Based on the anonymous identifier, the certification authority can check the status revocation of the certificate. The certification authority answers the request to the identity provider which can then transmit it to the card.