Block Cipher Diffuser for Disk Encryption Speed
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Solution Overview
Problem
Current block ciphers lack sufficient diffusion properties and speed, making them unsuitable for secure disk encryption, as they allow attackers to manipulate plaintext by modifying ciphertext, and existing large-block ciphers like Bear, Lion, and Beast are either too slow or compromise diffusion during decryption.
Innovation Solution
A block cipher design incorporating an established cipher like AES with additional diffuser components that provide enhanced diffusion properties, ensuring that changes to ciphertext result in unpredictable plaintext modifications, thereby thwarting attacker manipulation, and maintaining the security assurance of the underlying cipher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If AES-CBC is used for disk encryption, then the encryption is widely accepted and efficient, but the diffusion property is insufficient allowing attackers to flip arbitrary bits in plaintext
Solution Approach 1:
The patent combines AES-CBC encryption with an additional diffusion layer using a large-block cipher construction. This composite approach integrates the speed and security of AES with the enhanced diffusion properties of the new cipher structure, creating a hybrid system that leverages the strengths of both components.
Solution Approach 2:
The cipher divides the data block into two unequal parts and processes them through multiple rounds of encryption with different operations. This segmentation allows each part to be transformed independently through keyed hash functions and stream ciphers, achieving better diffusion while maintaining efficiency.
2Reliability
If Bear or Lion ciphers are used to achieve large block size and good diffusion, then the diffusion property is improved, but the encryption speed becomes too slow
Solution Approach 1:
The patent uses a 3-round Luby-Rackoff construction with partial processing in the final round. The last round applies a keyed hash function to only part of the data block rather than the entire block, reducing the total computational effort while maintaining sufficient diffusion properties for security.
Solution Approach 2:
The cipher varies the block size parameter to be sufficiently large (e.g., 512 bytes or more) to provide good diffusion, while adjusting the number of rounds and processing steps to optimize speed. This parameter optimization balances security requirements with performance constraints.
3Productivity
If Beast cipher is used to improve speed by replacing the last round, then the encryption speed increases, but the diffusion property is destroyed
Solution Approach 1:
The patent applies partial processing in the final round by using a keyed hash function on a portion of the data block rather than the entire block. This partial action maintains sufficient diffusion for security while reducing the computational overhead to improve encryption speed.
Data Source
AI summary
Encryption is provided with additional diffusion components to construct a block cipher with a large and variable block size. The cipher incorporates an encryption system or algorithm such that the cipher is at least as secure as the encryption system or algorithm. Additional components of the cipher provide improved diffusion. This combination ensures that the cipher is at least as strong as the encryption algorithm, and at the same time it provides additional security properties due to its improved diffusion.