DES Algorithm Protection via Dummy Key Hashing
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Solution Overview
Problem
DES-type ciphering algorithms are vulnerable to differential power analysis attacks, which can reveal the secret key by correlating intermediary results with integrated circuit power consumption, and existing solutions either require modifying the algorithm or introduce inefficiencies like pre-storing dummy keys.
Innovation Solution
The method involves executing the ciphering algorithm multiple times with dummy keys generated by applying a non-linear one-way function to the valid key, particularly focusing on the first and last iterations, and using a hash function to create these dummy keys, ensuring the real key is only stored securely without pre-storing dummy keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dummy keys are pre-stored to protect against differential power analysis attacks, then security is improved, but device complexity and memory requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-computing dummy keys through a one-way function during the initialization phase and storing them in a lookup table before the actual encryption operation begins. This allows the system to have protection ready in advance without adding complexity during the critical encryption path.
Solution Approach 2:
The patent introduces an intermediary mechanism - a one-way function and lookup table - that mediates between the secret key and the encryption process. The dummy keys act as intermediaries that mask the real key's power consumption signature without requiring modification of the core DES algorithm.
2Reliability
If the algorithm is modified to protect against differential power analysis, then security is improved, but ease of manufacture and compatibility decrease
Solution Approach 1:
The patent segments the protection mechanism from the core DES algorithm by implementing it as a separate preprocessing layer. The dummy key generation and selection is handled independently through a one-way function and lookup table, while the main DES encryption routine remains unchanged and can be manufactured using standard cells.
Solution Approach 2:
The patent creates copies of the key (dummy keys) through a one-way function that preserves the essential properties needed for encryption while being computationally infeasible to reverse. These copied keys can be used in place of the real key without modifying the encryption algorithm itself.
3Reliability
If multiple dummy keys are used to mask the real key, then security against differential power analysis is improved, but processing time increases
Solution Approach 1:
The patent performs the time-consuming operation of generating multiple dummy keys through the one-way function in advance, during system initialization. The results are cached in a lookup table, so that during actual encryption operations, the system only needs to perform a fast table lookup and selection, minimizing the time penalty.
Solution Approach 2:
The patent introduces dynamic key selection where the choice of which dummy key to use varies based on the actual input data being encrypted. This dynamic approach ensures that power consumption patterns do not correlate with the secret key while allowing the system to adapt to different encryption scenarios.
Data Source
AI summary
A method for protecting an execution, by an integrated circuit, of a ciphering and/or deciphering algorithm taking into account data and at least one valid key and performing several iterations of the same calculation, including at least one execution of an iteration with the valid key between several executions of the same iteration with the invalid keys obtained by applying at least one non-linear one-way function to the valid key.