Hybrid Email Content Protection with KACLS Key Isolation
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Solution Overview
Problem
Existing client-side encryption schemes require users to maintain and manage private keys across multiple devices, increasing the risk of key compromise and exposure, and message servers have access to unencrypted messages.
Innovation Solution
A hybrid content protection architecture using a trusted Key Access Control List Server (KACLS) that is separate from message servers, ensuring only the KACLS has access to private keys, allowing users to decrypt messages without exposing the keys to the message server or multiple devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If client-side encryption is used to maximize privacy, then message confidentiality is improved, but key management complexity and exposure risk increase
Solution Approach 1:
The patent introduces a Key Access Control List Server (KACLS) as an intermediary between users and message servers. The KACLS manages private keys centrally, allowing users to decrypt messages without maintaining keys across multiple devices. This mediator resolves the contradiction by preserving message confidentiality through encryption while eliminating the complexity of distributed key management.
Solution Approach 2:
The patent extracts the key management function from individual user devices and centralizes it in the KACLS. By taking out the private key storage and management responsibility from multiple user devices, the system maintains message confidentiality while reducing key management complexity and exposure risk at the device level.
2Ease of operation
If private keys are stored on multiple user devices for decryption capability, then message accessibility is improved, but key compromise risk increases
Solution Approach 1:
The KACLS acts as an intermediary that provides decryption capability without requiring private keys to be stored on multiple devices. Users can access and decrypt messages through the KACLS, which retrieves the necessary decryption keys temporarily. This maintains message accessibility while eliminating the security risk of distributing private keys across multiple devices.
Solution Approach 2:
The system uses temporary, single-use decryption keys that are generated and discarded as needed. Instead of storing persistent private keys on multiple devices, the KACLS generates short-lived decryption credentials that expire after use, reducing the window of opportunity for key compromise while maintaining message accessibility.
3Productivity
If message servers store unencrypted messages for delivery, then message delivery functionality is improved, but message security deteriorates
Solution Approach 1:
The patent segments the message into encrypted components that can be stored and transmitted separately. The message body and attachments are encrypted before storage on the message server, allowing the server to perform delivery functions while the encrypted nature of the data maintains security. The KACLS handles key management separately, enabling delivery functionality without compromising message security.
Data Source
AI summary
A computer-implemented method when executed by data processing hardware of a user device causes the data processing hardware to perform operations. The operations include obtaining, from a message server, an encrypted message encrypted by a single-use data encryption key (DEK) and an encrypted DEK including the single-use DEK encrypted by a public key (PK). The operations also include transmitting, to a key access control list server (KACLS), a decryption request requesting the KACLS decrypt the encrypted DEK with a PRK associated with the PK. The decryption request includes the encrypted DEK. The KACLS is independent from the message server. The operations also include receiving, from the KACLS, the single-use DEK and decrypting, using the single-use DEK, the encrypted message.