Secure Escrow Service for Cross-Device Keybag Restoration
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Solution Overview
Problem
Existing electronic devices face challenges in securely restoring encrypted keybags from one device to another due to UID-based encryption, which prevents decryption on devices with different Unique Device Identifiers (UIDs), leading to inaccessible confidential information in case of device loss, theft, or replacement.
Innovation Solution
The implementation of a secure escrow service that encrypts the recovery key with a user-specific escrow key, further encrypting it with a public key of highly secure servers, and requires authentication using username, password, and secret questions to decrypt and transfer the recovery key to a new device, ensuring only authorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the keybag is encrypted with the UID of the first device, then the security of the keybag is improved, but the ability to restore the keybag to a different device is lost
Solution Approach 1:
The encryption scheme is segmented into multiple layers: the keybag is encrypted with the first device's UID, and separately, a recovery key is encrypted with both the first device's UID and the second device's UID. This segmentation allows the keybag to remain securely tied to the original device while enabling restoration to a different device through the recovery key mechanism.
Solution Approach 2:
A recovery key acts as an intermediary element that bridges the security requirement (UID-based encryption) and the restoration requirement (access from different device). The recovery key is encrypted with multiple UIDs and serves as a mediator that enables authorized restoration without compromising the original security model.
2Adaptability or versatility
If the recovery key is encrypted with multiple UIDs, then the ability to restore across devices is improved, but the security against unauthorized access is reduced
Solution Approach 1:
Different parts of the encryption scheme have different security properties: the keybag itself remains encrypted with a single UID (high security, low adaptability), while the recovery key is encrypted with multiple UIDs (lower security, high adaptability). This local differentiation allows each component to optimize for its specific function.
Solution Approach 2:
The recovery key encryption uses excessive action by encrypting with multiple UIDs beyond what is minimally required for a single-device system. This partial relaxation of security (encrypting with multiple UIDs instead of one) enables the restoration functionality while maintaining adequate security through the multi-layered approach.
3Ease of operation
If unlimited retry attempts are allowed for decryption, then the ease of recovery is improved, but the vulnerability to brute force attacks is increased
Solution Approach 1:
The system implements periodic action through geometric timeouts that increase after each failed decryption attempt. Instead of allowing unlimited continuous retries, the system introduces increasing delays (periodic action with increasing period) that eventually prevent brute force attacks while still allowing legitimate users reasonable recovery opportunities.
Solution Approach 2:
The retry mechanism is dynamic rather than static: the timeout period dynamically increases with each failed attempt. This dynamic adjustment balances ease of recovery (allowing retries) with security (increasing difficulty over time), adapting the system's response based on the pattern of attempts.
Data Source
AI summary
A method of restoring confidential information items of a first device to a second device by using a set of servers. The method generates a public and private key pair and ties the private key to the hash of executable code of the servers at the time of generating the public and private keys. The method receives the encrypted confidential information items in a secure object which is encrypted with a user-specific key and the public key. The method only provides the confidential information to the second device when the second device provides the same user-specific key as the key that encrypts the secure object and the hash of the executable code of the servers at the time of accessing the private key to decrypt the secure object matches the hash of the executable code running on the servers at the time of generating the private key.