Verifiable Implicit Certificates via Ephemeral Key Binding
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Solution Overview
Problem
Existing implicitly certified public key schemes are vulnerable to inadvertent and malicious modification due to the insecure transmission of identity and public key reconstruction data, which compromises the security and integrity of the key establishment process.
Innovation Solution
A protocol that combines ephemeral public keys of each party to generate public key reconstruction data, encrypts this combination with the identity, and uses a signature scheme to create certificate components, allowing the derivation of a private key while ensuring the integrity of the certificate components through verification protocols, particularly implemented in an elliptic curve cryptosystem using point addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If identity and public key reconstruction data are transmitted in clear text, then the protocol is simpler and faster, but the security and integrity are compromised due to vulnerability to modification
Solution Approach 1:
The trusted authority performs preliminary actions by generating and signing the implicit certificate before transmission. The authority combines the identity, public key reconstruction data, and ephemeral public keys, then applies a digital signature to create a pre-validated certificate package. This preliminary signing ensures integrity and authenticity before the data leaves the trusted authority, eliminating the need for complex verification protocols at the receiving end while maintaining security.
Solution Approach 2:
A trusted authority acts as an intermediary between the key generation process and the final key establishment. The authority receives ephemeral public keys from parties, combines them with identity information, signs the resulting implicit certificate, and returns it. This intermediary role centralizes the security-critical functions of validation and signing, simplifying the overall protocol while ensuring reliability through the trusted mediator's cryptographic operations.
2Reliability
If a trusted authority signs and encrypts the combination of identity and public key reconstruction data, then tampering is prevented, but the computational overhead and processing time increase
Solution Approach 1:
The trusted authority performs the computationally intensive signing and encryption operations in advance, during the certificate generation phase. By completing these security-critical operations before transmission, the receiving parties only need to perform verification operations, which are computationally less intensive. This preliminary processing shifts the computational burden to the authority, reducing the time required at the receiving end.
Solution Approach 2:
The implicit certificate structure allows for efficient copying and verification. The signed and encrypted combination of identity and public key reconstruction data is created once by the trusted authority and can be verified multiple times by different parties without additional computational overhead for the original signing operation. The certificate serves as a reusable, self-contained verification package.
Data Source
AI summary
An implicit certificate cryptosystem uses an implicit certificate that includes a pair of certificate components. One of the certificate components includes a public key reconstruction data that is the combination of ephemeral public keys of two entities, one of which is a trusted entity and the other of which is associated with the implicit certificate. The public key reconstruction data is then combined with the identity of the other entity and the combination encrypted to form a first certificate component. A second certificate component is generated by using the first certificate component as a message in a signature scheme and generating a signature of the trusted entity on the message. The two certificate components are provided to the other entity to permit the other entity to generate a private key using one of the certificate components. The corresponding public key can be derived from the remaining certificate component.