Intermediate State Signature for Encrypted Data Integrity

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Solution Overview

Problem

Existing methods for protecting the confidentiality and integrity of data stored in external memory are inefficient in terms of space usage and processing time, and are vulnerable to replay attacks that can break encryption secrets.

Innovation Solution

A method that generates a signature from an intermediate state of the encryption algorithm, which is then stored alongside the encrypted data, allowing for efficient integrity verification without the need for additional random labels, and combining signatures with data before encryption to reduce memory requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If random labels are added to data before encryption for integrity protection, then data integrity and confidentiality are improved, but memory space consumption and processing time increase

Engineering Contradiction:
Improvedata integrityVSAvoidmemory space
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent extracts only the essential intermediate state from the encryption process to generate the signature, rather than using full random labels. This extraction approach reduces the amount of additional data stored in memory while maintaining integrity verification capability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The signature is generated during the encryption process itself by sampling intermediate states, rather than adding separate random labels afterward. This preliminary action integrates the integrity protection into the existing encryption workflow, avoiding additional memory overhead.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If random labels are added to data before encryption for integrity protection, then data integrity and confidentiality are improved, but processing time increases

Engineering Contradiction:
Improvedata integrityVSAvoidprocessing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent merges the integrity verification mechanism with the encryption process by generating signatures from intermediate states during encryption. This combination eliminates the need for separate label generation and processing steps, reducing overall processing time.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The signature generation is performed as a preliminary action during the encryption process itself, utilizing intermediate states that are already computed. This approach avoids additional processing time that would be required if separate integrity protection mechanisms were applied after encryption.

Inventive Principle:
Principle #10Preliminary action

3Quantity of substance

If intermediate state sampling is performed during encryption for signature generation, then memory space and processing time are reduced, but security against replay attacks must be maintained

Engineering Contradiction:
Improvememory spaceVSAvoidreplay attack vulnerability
Core Design Contradiction:
Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The intermediate state of the encryption algorithm serves as an intermediary element that binds the signature to the specific encrypted data. This intermediary ensures that any modification to the encrypted data will result in a mismatched signature, providing protection against replay attacks while using minimal memory.

Inventive Principle:
Principle #24Intermediary (Mediator)

4Quantity of substance

If multiple signatures are grouped and encrypted before storage, then memory efficiency is improved, but verification complexity increases

Engineering Contradiction:
Improvememory spaceVSAvoidverification process
Core Design Contradiction:
Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent segments the verification process into two phases: decryption/decryption of grouped signatures, then individual verification against intermediate states. This segmentation allows efficient memory usage through grouping while maintaining manageable verification complexity through structured processing steps.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP2166696B1protection of encrypted data Integrity using an intermediate cipher state to generate a signature
Publication Date: 2016.10.05 STMICROELECTRONICS (ROUSSET) SAS
  • EP2166696B1 patent drawingFigure 1~3
  • EP2166696B1 patent drawingFigure 4~6
  • EP2166696B1 patent drawingFigure 7~8B

AI summary

The invention relates to a method for protecting the integrity of encrypted data (CDATA) by an encryption algorithm providing at least one intermediate state intended to be identical in encryption and decryption, this intermediate state (ISTATE) being taken during encryption to generate a signature (T).