White-Box Cryptography Single Key Authorization
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Solution Overview
Problem
In the context of digital content distribution, existing technologies face challenges in securing copyrighted content due to the increasing complexity of user devices and networks, where attackers can modify and control software, making it difficult to enforce authorization and protect cryptographic functions.
Innovation Solution
A cryptographic system that uses a single cryptographic key to provide separate authorization for multiple input message groups by modifying the cryptographic implementation to produce incorrect outputs or terminate operations for unauthorized messages, utilizing a network of lookup tables and finite state machines, such as in a white-box implementation of AES or DES, to ensure secure and tamper-resistant operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cryptographic key is used for multiple input message groups, then device complexity and key management overhead are reduced, but authorization control and security enforcement become more difficult
Solution Approach 1:
The patent segments the input message space into distinct groups (e.g., different content types, access levels, or service categories) that can be identified by specific characteristics in the input message. Each group is associated with authorization parameters that define which cryptographic operations are permitted. This segmentation allows the system to enforce fine-grained authorization control using a single key, as the authorization decisions are made based on message group identification rather than key selection.
2Adaptability or versatility
If white-box cryptography is used to hide secret information in software, then flexibility and renewability are improved, but vulnerability to reverse engineering and tampering increases
Solution Approach 1:
The patent introduces an intermediary authorization layer between the input message and the cryptographic operation. This authorization module acts as a mediator that inspects the input message, identifies its group, verifies authorization parameters, and then permits or blocks the cryptographic operation. This intermediary structure allows the secret cryptographic key to remain hidden in software while adding a controllable access layer that can be renewed or modified without exposing the key, thereby reducing reverse engineering vulnerability while maintaining software flexibility.
3Reliability
If authorization control is strengthened for multiple message groups, then security enforcement improves, but processing overhead and operational complexity increase
Solution Approach 1:
The patent performs preliminary authorization validation by identifying the input message group and checking authorization parameters before the actual cryptographic operation occurs. This preliminary action filters out unauthorized messages early in the processing pipeline, preventing unnecessary cryptographic computations. By performing this group identification and authorization check beforehand, the system maintains strong security enforcement while improving processing efficiency, as unauthorized messages are rejected without consuming cryptographic processing resources.
Data Source
AI summary
A method of authorization in a cryptographic system that provides separate authorization for a plurality of different input message groups using a single cryptographic key, including: receiving, by the cryptographic system, a first input message from a first input message group; performing, by the cryptographic system, a keyed cryptographic operation mapping the first input message into a first output message, wherein the keyed cryptographic operation produces a correct output message when the cryptographic system is authorized for the first input message group, wherein the keyed cryptographic operation does not produce a correct output when the cryptographic system is not authorized for the first input message group, and wherein each of the plurality of input message groups has an associated set of input messages wherein the sets of input messages do not overlap.