Forward Secrecy via Blinded Key Exchange
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Solution Overview
Problem
Existing secure communication systems face challenges in preventing the tracking of computers during key exchanges, maintaining non-repudiation, and ensuring perfect forward secrecy, especially when static public keys are sent unencrypted, making them vulnerable to interception and decryption by attackers.
Innovation Solution
The use of ephemeral key pairs and blinding factors to create non-traceable, non-repudiable, and perfectly forward-secure communication channels by encrypting messages with shared secrets generated from ephemeral and static keys, ensuring that only the intended parties can decrypt and authenticate messages without revealing their identities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If static public keys are sent unencrypted during key exchange, then authentication is enabled, but computers can be tracked and their identities inferred by attackers
Solution Approach 1:
The patent segments the key exchange process into multiple stages: initial unencrypted public key exchange for authentication, followed by encrypted subsequent exchanges using derived session keys. This allows authentication to occur without exposing long-term private keys, preventing tracking while maintaining reliability.
Solution Approach 2:
The patent performs preliminary authentication using static public keys before establishing ephemeral session keys. This preliminary action enables identity verification without compromising long-term security, as the static keys are used only for initial handshake and not for encrypting subsequent communications.
2Productivity
If encryption keys are reused for multiple communications, then communication efficiency is improved, but past communications can be decrypted if keys are later compromised
Solution Approach 1:
The patent implements dynamic key derivation where session keys are generated fresh for each communication session using ephemeral key pairs. The session keys are derived from the static key material combined with session-specific random values, ensuring that compromise of one session's keys does not affect other sessions while maintaining efficient encrypted communication.
Solution Approach 2:
The patent uses disposable ephemeral key pairs for each communication session. These temporary keys are generated, used for that specific session's encryption, and then discarded. This approach provides perfect forward secrecy because each session's security is independent, yet maintains efficiency by deriving these temporary keys from pre-shared static key material.
3Loss of information
If blinding factors are used to hide public keys, then non-traceability is achieved, but authentication complexity increases
Solution Approach 1:
The patent uses blinding factors as cryptographic intermediaries that temporarily obscure public keys during exchange. These blinding factors are combined with the static public keys to create blinded versions for transmission, preventing tracking. The receiving party can verify authentication by unblinding the keys using their private key, maintaining security without excessive complexity.
Data Source
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AI summary
Embodiments of the invention can establish secure communications using a single non-traceable request message from a first computer and a single non-traceable response message from a second computer. Non-traceability may be provided through the use of blinding factors. The request and response messages can also include signatures that provide for non-repudiation. In addition, the encryption of the request and response message is not based on the static keys pairs, which are used for validation of the signatures. As such, perfect forward secrecy is maintained.