Ciphertext Key Storage for Post-Reset External File Access
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Solution Overview
Problem
Electronic devices face the issue of data in external memory being encrypted and deleted during a factory reset, rendering the data inaccessible due to the deletion of the encryption key stored in an erasable partition.
Innovation Solution
A method involving the encryption of a first key using an eigenvalue of an account identifier to generate a first ciphertext, followed by encrypting this eigenvalue to create a second ciphertext, both stored in a non-erasable partition, ensuring the data remains secure and accessible post-factory reset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the encryption key is stored in an erasable partition to enable factory reset, then the device can be reset to factory settings, but the encrypted data in external memory becomes inaccessible
Solution Approach 1:
The patent divides the storage system into two distinct partitions: an erasable partition for storing the encryption key (enabling factory reset) and a non-erasable partition for storing encrypted data (preserving data accessibility). This segmentation allows the system to independently manage key deletion and data retention, resolving the contradiction between reset capability and data accessibility.
Solution Approach 2:
The patent performs preliminary encryption of data before storage, using a key stored in the erasable partition. The encrypted data is then moved to the non-erasable partition. This preliminary action ensures that even if the key is deleted during factory reset, the encrypted data remains intact and can be recovered using backup mechanisms.
2Object-affected harmful factors
If the encryption key is deleted during factory reset to clear device data, then security is improved by removing access credentials, but the ability to decrypt external memory data is lost
Solution Approach 1:
The patent separates key storage from data storage by using different partition types. The encryption key is stored in the erasable partition (deleted during factory reset for security), while encrypted data is stored in the non-erasable partition (preserved for potential recovery). This segmentation allows selective deletion of keys without permanently losing encrypted data.
Solution Approach 2:
The patent introduces a backup mechanism that acts as an intermediary between the deleted key and the encrypted data. The backup stores encrypted data in a format that can be recovered even after key deletion, serving as a mediator that preserves data accessibility despite key removal for security purposes.
3Object-affected harmful factors
If data is encrypted in external memory for security, then data protection is improved, but data recovery after key deletion becomes impossible
Solution Approach 1:
The patent performs preliminary encryption of data before transferring it to external memory storage. The data is encrypted using a key that is subsequently stored in the erasable partition and backed up to the non-erasable partition. This preliminary action ensures that encrypted data can be recovered even after key deletion, as the backup contains the necessary encrypted information.
Solution Approach 2:
The patent creates a backup copy of encrypted data in the non-erasable partition. This copy serves as a redundant version that can be recovered even if the original key is deleted. The copying mechanism preserves data recoverability while maintaining the security benefits of encryption.
Data Source
AI summary
This application provides a method for saving a ciphertext and an apparatus. The method includes: obtaining an encryption instruction, where the encryption instruction instructs to encrypt a file in an external memory; obtaining an eigenvalue of a first account identifier based on the encryption instruction; encrypting a first key by using the eigenvalue of the first account identifier to generate a first ciphertext, where the first key is used to encrypt a second key, and the second key is used to encrypt a first file in the external memory; encrypting the eigenvalue of the first account identifier to generate a second ciphertext; and storing the first ciphertext and the second ciphertext in a non-erasable partition.