Encrypted Conversation History Access via Key Ciphertext Chaining
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Solution Overview
Problem
Existing systems face challenges in efficiently and securely granting selective access to an encrypted conversation history, particularly when different parts of the conversation are encrypted with different message keys, making it difficult for users to access the history without compromising security.
Innovation Solution
A method where client devices generate secret keys by hashing message keys and create key ciphertexts, storing only the latest secret key, allowing selective access by transmitting a single secret key to a target user to decrypt the conversation history.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple message keys are used to encrypt different parts of conversation history, then security is improved, but access control complexity increases
Solution Approach 1:
The patent segments the conversation history into multiple time periods, each encrypted with a different message key. It introduces a key ciphertext structure that links these segmented encryption keys to a master secret key, allowing selective access to specific time periods without compromising the entire conversation history. This segmentation approach maintains security while enabling granular access control.
Solution Approach 2:
The patent introduces a key ciphertext as an intermediary element between the master secret key and individual message keys. The key ciphertext contains encrypted message keys that can be decrypted using the master secret key, serving as a mediator that enables selective access to specific conversation periods without requiring distribution of all message keys to authorized users.
2Ease of operation
If all message keys are stored on client devices, then accessibility is improved, but memory usage increases
Solution Approach 1:
The patent extracts only the necessary information (key ciphertext) from the full set of message keys and stores it on client devices. The key ciphertext is a compact representation that, when decrypted with the master secret key, provides access to specific message keys for specific time periods. This extraction approach significantly reduces memory usage while maintaining accessibility to conversation history.
Solution Approach 2:
Instead of storing all message keys permanently on client devices, the patent implements a partial action by storing only the key ciphertext and master secret key. Users can access specific conversation periods as needed, decrypting only the necessary message keys at the time of access rather than having all keys stored simultaneously. This reduces memory requirements while maintaining functionality.
3Loss of information
If complete conversation history is transmitted to target user, then access completeness is improved, but bandwidth consumption increases
Solution Approach 1:
The patent segments the conversation history into distinct time periods, each with its own message key and key ciphertext. When granting access to a target user, the system transmits only the key ciphertext corresponding to the specific time period(s) the user needs access to, rather than transmitting the entire conversation history. This segmentation approach maintains information completeness for the requested period while significantly reducing bandwidth consumption.
Solution Approach 2:
The patent applies local quality by providing different levels of access to different parts of the conversation history. Each time period has its own key ciphertext that can be independently transmitted and decrypted. This allows the system to transmit only the locally relevant portion of the conversation history to the target user, optimizing bandwidth usage while maintaining complete access to the requested time period.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces processing power, bandwidth, and memory usage while ensuring secure and efficient access to encrypted conversation history by allowing targeted access based on the provided secret key.
Implementation Method 1
determining a current secret key by hashing the prior secret key and the message key
Implementation Method 2
generating the key ciphertext by encrypting the prior secret key and the message key using the current secret key
Data Source
AI summary
Selective access to an encrypted conversation history can be granted as described herein. For example, a first client device can determine a message key used to encrypt messages associated with a conversation. The first client device can then generate a key ciphertext by: determining a prior secret key, determining a current secret key by hashing the prior secret key and the message key, and generating the key ciphertext by encrypting the prior secret key and the message key using the current secret key. The first client device can then transmit the key ciphertext to a server system. To grant the second client device with access to the encrypted messages, the first client device can transmit the current secret key to the second client device, which can obtain the key ciphertext from the server system and apply the current secret key to derive the message key and decrypt the messages.