Mutually Authenticated ECDHE Key Exchange Using Key Server
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Solution Overview
Problem
Existing ephemeral elliptic curve Diffie-Hellman key exchange (ECDHE) systems lack mutual authentication, are susceptible to 'man in the middle' attacks, and face security risks due to the repeated use of static PKI keys, which compromises forward secrecy and scalability, especially in large networks where recording and operating static private keys are insecure.
Innovation Solution
A system that enables mutually authenticated ECDHE key exchanges using a key server, where devices and servers record and operate compatible values and algorithms for key pair generation, ECDH key exchange, and symmetric ciphering, without requiring the recording of static private keys, thereby enhancing security and scalability by using a key server to manage network static private keys securely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If devices and servers record and operate static PKI keys for ECDHE key exchange, then mutual authentication can be achieved, but security is compromised due to the insecure storage and management of static private keys
Solution Approach 1:
The patent extracts the static private key management function from the device and server, placing it in a dedicated key server. This separation removes the harmful factor of insecure local key storage while preserving the authentication function. The key server becomes a trusted third party that manages static keys securely, allowing devices and servers to authenticate without locally storing private keys.
Solution Approach 2:
The key server acts as an intermediary between devices and servers, managing the static PKI keys. Instead of devices and servers directly storing and using static private keys, they interact with the key server which mediates key management operations. This intermediary approach resolves the contradiction by providing secure key management while enabling authentication.
2Reliability
If devices and servers store static private keys locally, then authentication can be performed, but scalability is limited due to the security burden on each node
Solution Approach 1:
The patent extracts the key management burden from individual nodes (devices and servers) and centralizes it in a key server. This extraction enables scalability by removing the security burden from each node, allowing the network to grow without proportionally increasing the security complexity at each endpoint.
Solution Approach 2:
The key server provides a universal key management service that can serve multiple devices and servers. Instead of each node independently managing its own static keys, the key server provides a multi-functional key management capability that supports authentication for the entire network, enhancing scalability.
3Ease of operation
If the same static PKI key pair is reused for multiple ECDHE key exchanges, then implementation is simplified, but forward secrecy is compromised
Solution Approach 1:
The patent introduces dynamic ephemeral key pairs for each ECDHE key exchange while maintaining static key pairs for authentication. This dynamic approach ensures that even if static keys are compromised, past and future sessions remain secure through the use of unique ephemeral keys for each exchange, preserving forward secrecy while maintaining implementation simplicity through key server management.
Data Source
AI summary
A device can (i) store public keys Ss and Sn for a network and (ii) record private key sd. A network can record a corresponding private keys ss and sn. The device can (i) generate a device ephemeral PKI key pair (Ed, ed) and (ii) send public key Ed to the network. The device can receive an ephemeral public key Es from the network. The device can calculate values for A: an elliptic curve point addition over Ss, Sn, and Es, and B: (sd+ed) mod n. The device can input values for X and Y into an elliptic curve Diffie Hellman key exchange (ECDH) in order to determine a mutually derived shared secret X5, where the network can also derive shared secret X5. The device can (i) use X5 to derive a key K2 and (ii) decrypt a ciphertext from the network using key K2.