Key Transparency Server for Secure Messaging
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Solution Overview
Problem
Existing messaging systems face challenges in securely routing messages across multiple devices, as unauthorized actors can attempt to register devices without user permission, potentially intercepting communications by deceiving the system into sending messages to unauthorized devices.
Innovation Solution
A secure message exchanging system that employs a key transparency server and cloud-based storage to verify and validate public keys, using cryptographic techniques such as digital signatures and Merkle trees to ensure only authorized devices can register and receive encrypted messages, thereby preventing unauthorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a registration service is used to facilitate cryptographic exchange, then message routing capability is improved, but security against unauthorized registration is worsened
Solution Approach 1:
A key transparency server is introduced as an intermediary between the registration service and devices. This server maintains a transparency log that records all public key registrations, allowing any device to verify whether a public key has been legitimately registered. The intermediary provides verification capability without interfering with the original registration process, thus maintaining routing capability while adding security verification.
Solution Approach 2:
The system implements a feedback mechanism where the key transparency server provides verification responses to devices querying about registered public keys. This feedback loop allows devices to confirm the legitimacy of registration information before establishing cryptographic connections, creating a closed-loop verification system that prevents unauthorized registration while maintaining smooth message routing.
2Ease of operation
If public keys are distributed through a centralized service, then ease of message exchange is improved, but vulnerability to unauthorized access is worsened
Solution Approach 1:
The system performs preliminary verification of public keys against the transparency log before establishing message exchange. Devices check whether public keys have been legitimately registered in advance of using them for encryption, preventing unauthorized keys from being used in message exchange. This preliminary action maintains ease of operation by automating verification while blocking unauthorized access attempts.
Solution Approach 2:
The key transparency server provides a mechanism for preliminary anti-action by allowing devices to verify the legitimacy of public keys before they can be exploited for unauthorized access. The transparency log serves as a pre-established reference that actively prevents unauthorized registration from succeeding, countering the vulnerability before it can be exploited.
3Productivity
If cryptographic information is stored centrally, then device registration efficiency is improved, but risk of key compromise is worsened
Solution Approach 1:
The system segments the cryptographic information storage function into two parts: the registration service maintains registration records for efficiency, while the key transparency server maintains the transparency log for verification. This segmentation allows efficient registration processing while distributing the security function, reducing the risk that compromise of a single central storage point would affect both registration efficiency and security equally.
Data Source
AI summary
Techniques are disclosed relating to secure message exchanges. In some embodiments, a first computing device generates an account key associated with a user account shared by a plurality of computing devices. The first computing device signs a public key of the first computing device with the generated account key to produce a digital signature and sends the public key and the digital signature to a first server system for distributing the public key to a second computing device attempting to send an encrypted message to the first computing device. The first computing device sends the account key to an external storage external usable by others of the plurality of computing devices to obtain the account key and use the account key to sign public keys of the other computing devices. The first computing device receives, from the second computing device, the encrypted message encrypted using the public key.