Mobile Device S/MIME Encryption via Piggybacked Key Retrieval
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Solution Overview
Problem
Public-key encryption systems in mobile devices face challenges when devices are offline, as they cannot retrieve public keys from messaging servers, limiting their ability to encrypt messages until they reconnect, which can delay message transmission and lead to incomplete communication.
Innovation Solution
A method that allows mobile devices to store encrypted messages offline and retrieve public keys during subsequent online sessions by piggybacking certificate queries on existing network connections, using the S/MIME encryption protocol to encrypt messages once keys are obtained, and storing unencrypted messages in a 'drafts' folder for later transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If public-key encryption is used to secure messages, then message security is improved, but the ability to send messages while offline is worsened because public keys cannot be retrieved
Solution Approach 1:
The system performs preliminary actions by storing encrypted messages in the outbox with a flag indicating encryption is needed, and by piggybacking certificate queries on synchronization requests before the device actually needs to send the message. This allows the device to prepare for encryption while offline, then execute the encryption when connectivity is restored without delaying message transmission.
2Reliability
If the device waits to retrieve public keys before sending messages, then encryption can be performed, but message transmission time is worsened due to delays
Solution Approach 1:
The system queries for certificates in advance by piggybacking the certificate request on the synchronization request that is already being made when the device goes online. This preliminary action ensures that the public keys are retrieved before the device needs to send messages, eliminating transmission delays while maintaining encryption capability.
Solution Approach 2:
The system maintains continuous operation by storing messages in the outbox with encryption flags during offline periods, then seamlessly transitioning to encryption execution when online. The piggybacking technique ensures that certificate retrieval continues without interrupting the synchronization process, maintaining useful action continuity and preventing time loss.
3Reliability
If the device always connects to the server to retrieve public keys, then encryption is reliable, but network dependency is worsened limiting offline functionality
Solution Approach 1:
The system performs preliminary actions by storing encrypted messages locally in the outbox with a flag indicating encryption is needed, and by piggybacking certificate queries on synchronization requests before the device actually needs to send the message. This allows the device to prepare for encryption while offline, then execute the encryption when connectivity is restored without delaying message transmission.
Solution Approach 2:
The system uses the synchronization request as an intermediary carrier to transport the certificate query. Instead of requiring a separate dedicated connection just for key retrieval, the certificate request is embedded within the existing synchronization traffic, enabling reliable key retrieval while maintaining offline functionality during periods when full synchronization isn't possible.
Data Source
AI summary
Systems and methods are disclosed that facilitate identifying messages generated on a mobile device while the device is offline as requiring encryption, storing the messages in a message outbox with a flag indicating that encryption is required, and identifying recipients of the flagged messages to generate a recipient list. The recipient list can be piggybacked on a server synchronization request when the mobile device enters a period of online activity, and a server can return public keys associated with identified recipients to permit an encryption component, such as a secure/multipurpose Internet mail extension protocol (S/MIME) encryption component, in the mobile device to encrypt the messages.