NAND Flash Memory PUF Encryption Key Generation
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Solution Overview
Problem
Conventional methods for protecting digital data, such as using digital identifiers and encryption, are inadequate as they can be circumvented by hackers, allowing unauthorized transfer of sensitive content like private digital images.
Innovation Solution
A method involving a physical unclonable function (PUF) is used, where a NAND flash memory array's physical properties are measured to generate a unique encryption key, and helper data is created to securely encrypt and decrypt digital content, ensuring it remains bound to an authorized device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If conventional encryption methods are used to protect digital data, then data confidentiality is improved, but security against hacking is worsened because keys stored in memory can be read by hackers
Solution Approach 1:
The patent extracts the key generation process from conventional memory storage and relocates it to the physical properties of the memory array itself. The encryption key is derived from analog values inherent to the physical characteristics of memory cells, removing the vulnerability of storing keys in accessible memory locations.
Solution Approach 2:
The patent introduces an intermediary process where physical properties of memory cells serve as a mediator between the hardware and cryptographic functions. Instead of directly storing keys in memory, the system uses physical characteristics (threshold voltages, leakage currents) as an intermediate layer that cannot be directly accessed or read by hackers.
2Ease of operation
If digital identifiers are used to authenticate users, then access control is improved, but security is worsened because authenticated users can freely transfer digital data
Solution Approach 1:
The patent segments the authentication system into two distinct components: a physical unclonable function (PUF) derived from memory array properties for device identification, and traditional digital identifiers for user authentication. This segmentation ensures that even with valid user credentials, data cannot be transferred without the specific physical device that generated the original encryption key.
Solution Approach 2:
The patent changes the fundamental parameter of authentication from solely digital credentials to a combination of physical device characteristics and digital identifiers. By incorporating physical properties (threshold voltages, leakage currents) as immutable parameters, the system prevents unauthorized data transfer while maintaining ease of legitimate access.
3Ease of manufacture
If keys are stored in memory for encryption, then encryption functionality is improved, but security is worsened because memory keys can be circumvented by optical reading methods
Solution Approach 1:
The patent replaces the mechanical/electrical system of key storage in memory with a physical system based on inherent properties of memory cells. Instead of storing digital key values that can be optically read, the system uses physical characteristics (threshold voltages, leakage currents) that require physical interaction with the memory cells themselves, making optical attacks ineffective.
Solution Approach 2:
The patent converts the natural variability and imperfections in memory cell physical properties, which are typically considered manufacturing defects, into a security feature. These variations in threshold voltages and leakage currents, rather than being harmful, become the basis for generating unique, unclonable encryption keys that are resistant to hacking.
Data Source
AI summary
A method of encrypting unencrypted digital content includes measuring an analog value associated with a physical property of interested cells of a memory array; digitizing the measured analog value to generate a response key; generating an encryption key based at least on the response key; encrypting the unencrypted digital content to generated encrypted digital content based on the encryption key; and storing the encrypted digital content.