Post-Quantum Session Key Generation via Ephemeral Keys
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Solution Overview
Problem
The advent of quantum computers threatens to break existing key exchange mechanisms like X3DH, necessitating the development of post-quantum alternatives that face challenges in replacing Diffie-Hellman-like key exchanges and ensuring receiver-oblivious key exchanges for secure messaging.
Innovation Solution
A method for generating a session key using ephemeral keys, ciphertexts, and intermediate keys, where the session key is generated by encrypting a session identifier based on peer identifiers and public keys, utilizing post-quantum key encapsulation mechanisms and signature schemes to ensure security and anonymity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If post-quantum key encapsulation mechanisms are used to replace Diffie-Hellman, then quantum security is improved, but the complexity of implementing receiver-oblivious key exchanges worsens
Solution Approach 1:
The patent segments the key exchange process into distinct phases: a first phase where the first peer generates and transmits an ephemeral key, and a second phase where the second peer generates a ciphertext using the received ephemeral key. This segmentation allows each phase to be optimized independently, with the first phase focusing on key generation and the second phase focusing on ciphertext generation, thereby reducing overall implementation complexity while maintaining quantum security.
Solution Approach 2:
The patent introduces an ephemeral key as an intermediary element that facilitates the key exchange between peers. The first peer generates this ephemeral key and transmits it to the second peer, who then uses it to generate a ciphertext. This intermediary ephemeral key simplifies the interaction between the peers by providing a shared reference point that enables both to derive the session key without direct complex interactions.
2Ease of operation
If traditional Diffie-Hellman key exchange is used, then ease of implementation is maintained, but security against quantum computers deteriorates
Solution Approach 1:
The patent changes the mathematical parameters underlying the key exchange from traditional Diffie-Hellman to post-quantum key encapsulation mechanisms. Specifically, it uses lattice-based cryptography parameters (such as those in the NIST PQC competition) that are resistant to quantum attacks. This parameter change maintains the general structure and ease of implementation of key exchange protocols while providing security against quantum computers.
3Loss of information
If receiver-oblivious key exchange is implemented, then anonymity is improved, but the complexity of key generation worsens
Solution Approach 1:
The patent performs preliminary actions by having the first peer generate and transmit an ephemeral key before the actual key exchange begins. This preliminary ephemeral key serves as a foundation that the second peer can use to generate the ciphertext without needing to know any additional information about the first peer. This preliminary action simplifies the subsequent key generation process while maintaining receiver-oblivious anonymity.
Data Source
AI summary
A key generation method is provided. A first peer obtains an ephemeral key from a second peer via a server. The first peer uses the ephemeral key to compute a ciphertext that encrypts a first parameter. The first peer uses the first parameter to generate a session key. The ciphertext is sent to the server by the first peer to allow the second peer to generate the session key. The key may be subsequently used for communication, such as by using a key management algorithm such as Double Rachet.