Automaton-Based String Authentication via Encrypted Key Chains
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Solution Overview
Problem
Existing authentication systems fail to securely determine whether an input string matches a pattern defined by an automaton without revealing the string or the automaton's state transitions to the other party.
Innovation Solution
A server-client system where the server generates and provides encrypted key chains based on automaton state transitions, and the client decrypts these chains to determine if the input string leads to a final accepted state, using privacy-preserving set-intersection protocols to conceal the input string and automaton state from each party.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the server directly evaluates the automaton state transitions for the input string, then the authentication result can be determined efficiently, but the input string and automaton state information are exposed to the client
Solution Approach 1:
The patent introduces encrypted key chains as an intermediary mechanism. The server generates encrypted key chains that encode automaton state transition information without exposing the actual string or state details. These key chains serve as a mediator that allows the client to verify authentication results while maintaining privacy, resolving the contradiction between security and information protection
Solution Approach 2:
The patent creates encrypted copies of the automaton state transition paths as key chains. Instead of transmitting the actual string or state information, the system transmits encrypted representations (copies) that can be verified without revealing the underlying data. This copying approach enables authentication verification while preventing information leakage
2Reliability
If the client decrypts all key chains to determine the final state, then the authentication can be completed, but the computational complexity increases with the number of key chains
Solution Approach 1:
The patent segments the authentication process into multiple independent key chains, each corresponding to a specific state transition path. Instead of processing a single complex authentication result, the system divides the automaton execution into discrete segments (key chains) that can be processed independently. This segmentation allows the client to manage complexity by handling smaller, modular decryption operations rather than a single large complex computation
Data Source
AI summary
Provided is a server connectable to a client for input of a string and that has an automaton defining a subsequent state for transition for each state and each character. This server has a key chain generating unit for generating a key chain for each combination of index, character and state expressing the position of each character in a string, the key chain having encrypted keys for the next index corresponding to the subsequent state of transition from the current state in accordance with the character on the basis of the key corresponding to the current state, and a providing unit for communicating with a client and providing to the client a key chain corresponding to each inputted key among a set of key chains for each index in a state concealing the inputted characters from the client.