Session Resumption Key Derivation Using One-Time Pad
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Solution Overview
Problem
Current cryptographic protocols for secure session resumption, such as TLS 1.3, are vulnerable to replay attacks and compromise forward secrecy due to the reuse of session keys, which can be intercepted and used to decrypt previous and future communications.
Innovation Solution
The method involves deriving a new key independently by the client and server using a one-time pad and session data, ensuring that each resumed session uses a unique key, preventing key reuse and interception, and employing a keyed hashing function to generate the new key for 0-RTT session resumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If session keys are reused for session resumption, then communication efficiency is improved, but security is worsened due to vulnerability to replay attacks and compromise of forward secrecy
Solution Approach 1:
The patent changes the key parameter from reused session keys to derived keys that are uniquely generated for each session resumption. The key derivation function incorporates session data and a one-time pad to generate a new key parameter for each session, preventing key reuse while maintaining efficient session resumption.
Solution Approach 2:
The patent employs a one-time pad that is discarded after use in each session resumption. This disposable cryptographic element ensures that once the key is derived and used, it cannot be reused, thereby preventing replay attacks and maintaining forward secrecy without requiring expensive long-term key management.
2Reliability
If a new key is derived for each session resumption, then security is improved by preventing replay attacks, but device complexity increases due to additional key derivation operations
Solution Approach 1:
The patent introduces a key derivation function as an intermediary that simplifies the complexity of generating unique keys for each session. This mediator function takes session data and a one-time pad as inputs and produces a derived key, abstracting away the cryptographic complexity while ensuring security.
Solution Approach 2:
The patent performs preliminary key derivation actions during the session resumption process itself, rather than requiring separate key generation steps. The key is derived on-demand using the session data and one-time pad, eliminating the need for pre-computed keys and reducing overall system complexity.
3Reliability
If session data and one-time pad are used to derive a new key, then forward secrecy is ensured, but loss of information occurs due to the need to discard previous session keys
Solution Approach 1:
The patent implements a strategy where previous session keys are discarded after use, and the one-time pad is discarded after deriving the new key. This discarding mechanism ensures forward secrecy by preventing recovery of previous keys, while the key derivation function recovers the necessary cryptographic material (new key) from the session data and one-time pad.
Data Source
AI summary
Session resumption for cryptographic communications is provided. Session data and encrypted early data are received from a client. A key is derived using the session data and a one-time pad. The early data is decrypted using the derived key.