Verifiable Encryption via Dynamic Key Derivation
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Solution Overview
Problem
Devices that use secret cryptographic keys are vulnerable to external monitoring attacks, such as differential power analysis, which can extract keys by monitoring external characteristics like operation timing and power consumption, especially when the same key is repeatedly used for different inputs, posing a risk of unauthorized access and data tampering.
Innovation Solution
The implementation of a verifiably secure encryption method where each data set is associated with a unique message identifier, and the encryption device derives a message key through an iterative process using a shared secret internal state, with each plaintext segment encrypted using different keys derived from the message key, and validators are computed to ensure data integrity and authenticity during decryption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same cryptographic key is repeatedly used for different inputs, then encryption efficiency is improved, but vulnerability to external monitoring attacks increases
Solution Approach 1:
The patent implements dynamic key derivation where a single master key is transformed into multiple different encryption keys through a key derivation function that incorporates a message identifier. This allows the system to efficiently encrypt multiple messages without repeatedly using the same key, thereby maintaining encryption efficiency while preventing key reuse vulnerabilities to external monitoring attacks.
Solution Approach 2:
The patent changes the parameter of the encryption key by deriving different keys from a master key using a key derivation function that takes a message identifier as input. This parameter transformation ensures that each encryption operation uses a unique key derived from the same master key, improving security against external monitoring while maintaining the efficiency of key management.
2Reliability
If physical shielding facilities are used to protect cryptographic systems, then protection against external monitoring attacks is improved, but cost and operational complexity increase
Solution Approach 1:
The patent replaces the mechanical/physical shielding system with a cryptographic software-based solution. Instead of using physically secure, shielded rooms to protect cryptographic operations, the patent uses a key derivation function that mathematically prevents external monitoring attacks through entropy redistribution and key differentiation, thereby eliminating the need for complex physical infrastructure.
Solution Approach 2:
The patent changes the approach from physical parameter protection (shielding, isolation) to cryptographic parameter protection (key derivation, entropy redistribution). This transformation allows the system to achieve the same security goal of protecting against external monitoring attacks without requiring expensive and complex physical facilities.
3Reliability
If key derivation methods are used to protect against external monitoring attacks, then security is improved, but the ability to store and manage sequence counters is required
Solution Approach 1:
The patent makes the message identifier serve multiple functions: it acts as both an index for key derivation and as a unique identifier for each encryption operation. This eliminates the need for separate sequence counters or additional storage mechanisms, as the message identifier itself provides the necessary information for both key differentiation and operation tracking.
Solution Approach 2:
The patent extracts the sequence counter functionality from the key derivation process and replaces it with a message identifier that is naturally present in the data being encrypted. This extraction eliminates the need for separate counter storage and management, reducing device complexity while maintaining security against external monitoring attacks.
Data Source
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AI summary
Methods and devices to encrypt and decrypt sensitive data to in a manner that provides secunty from external monitoring attacks is disclosed The encrypting device has access to a base secret cryptographic value (key) that is also known to the decrypting device The sensitive data are decomposed into segments, and each segment is encrypted with a separate encryption key denved from the base key and a message identifier to create a set of encrypted segments The encrypting device uses the base cryptographic value to create validators that prove that the encrypted segments for this message identifier were created by a device with access to the base key The decrypting device, upon receiving an encrypted segments uses validators to verify the message identifier and that the encrypted segment are unmodified.