Adjustment-Value Block Cipher Processing Reduction
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Solution Overview
Problem
Existing adjustment-value-attached block cipher modes, such as XE, XEX, and XEX*, require additional processing steps and resources, increasing the amount of processing needed for encryption compared to simple block cipher encryption, due to the requirement for exclusive-OR operations with offsets.
Innovation Solution
A block cipher apparatus and method that divides an adjustment value into two parts, encrypts one part to generate an offset, and then either adds or encrypts the plaintext based on this offset, allowing for reduced processing by omitting exclusive-OR operations on either the plaintext or ciphertext side, depending on the operation mode specified.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adjustment-value-attached block cipher modes (XE, XEX, XEX*) are used to provide security against chosen-plaintext and chosen-ciphertext attacks, then security is improved, but the amount of processing increases due to additional exclusive-OR operations with offsets
Solution Approach 1:
The adjustment value (tweak) is divided into two separate parts: a first adjustment value used for generating the offset, and a second adjustment value used for determining the final ciphertext. This segmentation allows the offset generation to be performed once and reused, reducing the total number of operations compared to traditional modes that require separate processing for each block.
Solution Approach 2:
The offset is generated in advance by encrypting the first adjustment value before the actual plaintext encryption occurs. This preliminary computation of the offset eliminates the need to perform exclusive-OR operations during the main encryption process, thereby reducing the processing amount while maintaining security.
2Reliability
If traditional adjustment-value-attached block cipher modes are used, then security is maintained, but the device complexity increases due to additional encryption sections and processing steps
Solution Approach 1:
The offset generation process is merged with the main encryption flow by using the same block cipher encryption section for both offset generation and plaintext encryption. This eliminates the need for separate dedicated offset generation hardware, reducing device complexity while maintaining the security properties of adjustment-value-attached block ciphers.
Data Source
AI summary
There is provided an adjustment-value-attached block cipher apparatus realizing block cipher processing that the amount of processing is small in adjustment-value-attached block cipher. The adjustment-value-attached block cipher apparatus includes: an encryption section performing encryption by a block cipher system; an input section accepting plaintext, an adjustment value and instruction information indicating first or second cipher processing; and a generator dividing the adjustment value into first and second adjustment values, encrypting the first adjustment value using the encryption section to generate cipher for offset, determining an offset value according to the cipher for offset and the second adjustment value, determining the sum of the offset value and the plaintext, and encrypting the sum using the encryption section to generate first ciphertext when the instruction information indicates the first cipher processing, and encrypting the plaintext using the encryption section to generate second ciphertext when the instruction information indicates the second cipher processing.