Augmented Random Oracle Model for Cryptographic Security

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Solution Overview

Problem

The random oracle model (ROM) has limitations, particularly in its inability to capture non-black-box techniques, leading to uninstantiability results where protocols proven secure in ROM are insecure when instantiated with real hash functions.

Innovation Solution

The Augmented Random Oracle Model (AROM) introduces a second oracle M to model non-black-box tools, allowing for the simulation of real hash functions and capturing a wide range of ROM impossibility results.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the Random Oracle Model (ROM) is used to analyze cryptographic protocol security, then security proofs can be obtained for protocols without standard model security proofs, but the proofs may be uninstantiable meaning the protocol is insecure under any instantiation of the hash function

Engineering Contradiction:

Improvesecurity proof validityVSAvoidinstantiation compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces a simulator S as an intermediary component between the random oracle O and the adversary A. This simulator acts as a mediator that programs the random oracle's responses based on the adversary's queries and internal state, enabling the reduction proof to work. The simulator translates adversary interactions into standard model attacks, bridging the gap between ROM security and standard model security.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the security proof into two distinct parts: a ROM proof that uses the random oracle model assumptions, and a standard model proof that instantiates the hash function with a concrete construction. This segmentation allows each proof to address different aspects of security, with the ROM proof capturing high-level security properties and the standard model proof ensuring instantiation compatibility.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If non-black-box techniques are used to prove ROM uninstantiability, then specific hash function code can be analyzed, but the techniques cannot be applied to random oracles which have no code

Engineering Contradiction:

Improvehash function analysis precisionVSAvoidapplicability to random oracles

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent creates a copy of the hash function code within the simulator S, allowing non-black-box analysis of the code structure while maintaining compatibility with random oracle semantics. The simulator contains and analyzes the hash function implementation, enabling precise code-level security analysis without preventing the random oracle from being treated as an abstract function with no external code.

Inventive Principle:

Principle #26Copying

3Productivity

If ROM proofs are used for cryptographic protocols, then efficiency is improved compared to standard model proofs, but security guarantees are weakened due to uninstantiability results

Engineering Contradiction:

Improvecryptographic protocol efficiencyVSAvoidsecurity guarantee strength

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent merges the efficiency benefits of ROM proofs with the security guarantees of standard model proofs by combining them into a unified security framework. The protocol can use ROM-based constructions for efficiency while the combined proof methodology ensures standard model security, eliminating the trade-off between efficiency and security guarantee strength.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12323513B1Enhanced security for public key cryptosystems from augmented random oracles

Publication Date: 2025.06.03 NTT RESEARCH INC

AI summary

A public key cryptosystem has enhanced security based on the use of an augmented random oracle model (AROM). The system includes corresponding encryption and decryption functionality.