Digital Certificate Revocation via Hash Chain and Redactable Signatures
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Solution Overview
Problem
Current digital certificate revocation methods, such as Certificate Revocation Lists (CRLs) and Certificate Revocation Trees (CRTs), face inefficiencies in communication, search, and verification costs, and centralized Certificate Authorities (CAs) become bottlenecks or compromise security when decentralized.
Innovation Solution
The NOVOMODO approach uses a hash chain and untrusted directories to provide unsigned validity status, allowing for efficient distribution of certificate validity proofs and reducing the need for CA involvement, while enabling secure verification without the CA's signing key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CRLs are used for certificate revocation, then certificate validity can be verified, but communication and verification costs increase significantly
Solution Approach 1:
The patent segments the monolithic CRL into hierarchical trees (CRTs) where revocation information is distributed across multiple levels. Each node in the tree contains only the revocation information necessary for that specific branch, allowing verifiers to download and process only the relevant portions rather than the entire CRL, thereby reducing communication and verification costs while maintaining reliability.
Solution Approach 2:
The patent extracts the essential revocation information from the full CRL and organizes it into a tree structure where only necessary data is retained at each level. This extraction eliminates redundant information that would otherwise need to be transmitted and processed, reducing the energy cost of verification while preserving the ability to verify certificate validity.
2Reliability
If centralized CA is used for certificate management, then security is maintained, but the CA becomes a validation bottleneck
Solution Approach 1:
The patent segments the centralized CA's validation function into a distributed hierarchical tree structure. Multiple CA instances can operate independently at different levels of the tree, allowing parallel validation operations. This segmentation maintains security through cryptographic signatures while eliminating the single-point bottleneck, thereby increasing validation throughput.
Solution Approach 2:
The patent transitions from a single-dimensional centralized validation model to a multi-dimensional hierarchical tree structure. Validation can occur at multiple levels and branches simultaneously, adding spatial and structural dimensions to the validation process. This enables parallel processing and increases throughput while maintaining security through the tree's cryptographic structure.
3Reliability
If CA signature is included in OCSP responses, then response authenticity is guaranteed, but signature length increases communication overhead
Solution Approach 1:
The patent extracts the CA's public key and signature algorithm information from the full OCSP response, placing them in the certificate structure itself. The OCSP response then contains only the essential validity information with compact references to the CA's signing key, reducing signature length and communication overhead while maintaining authenticity verification capability.
Solution Approach 2:
The patent makes the CA's public key and signing algorithm information universal by embedding them in the certificate structure where they can be reused across multiple OCSP responses. This eliminates the need to include redundant signature data in each response, reducing communication overhead while maintaining the ability to verify response authenticity through the embedded cryptographic material.
Data Source
AI summary
Different targets (c0, N1) of a digital certificate are mapped into a “super-target” using methods allowing a certificate validity verifier (110) to compute the super-target. The certificate includes the super-target instead of the targets. Also, a certificate with multiple targets can be signed with a redactable signature by the certification authority (CA 120). When the certificate's owner provides the certificate to a verifier together with a validity proof, the owner redacts the certificate to delete unnecessary targets. A single validity proof (ci(F)) may be provided to certificate owners for a set (F) of the certificates via a multicast transmission if a multicasting group (2010) is formed to correspond to the set.