Multi-Signer LMS Public Key Provisioning for Firewalled IoT Updates
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Solution Overview
Problem
Existing hash-based signature schemes are vulnerable to quantum computing attacks and require a centralized signing service, which can be inaccessible due to firewalls, compromising security and efficiency in firmware updates for IoT devices.
Innovation Solution
Implement a stateful hash-based signing system with a single public key and multiple independent signers, using a Leighton-Micali signature scheme combined with a Merkle tree structure, where each signer generates local keys and shares them with a provisioning server to create a common public key, enabling secure and efficient signing without reliance on a centralized service.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centralized signing service is used to implement hash-based signature schemes, then security against quantum attacks is improved, but accessibility and reliability deteriorate when firewalls are present
Solution Approach 1:
The patent segments the centralized signing service into multiple independent signers distributed across different locations. Each signer holds a portion of the signing capability (local private key) and can independently sign messages. This segmentation eliminates the single point of failure and accessibility issues associated with centralized services while maintaining security through the distributed nature of the system.
Solution Approach 2:
The patent merges multiple independent signers into a unified system that produces a single common public key. The signers collectively implement the hash-based signature scheme, combining their individual signing capabilities through the Merkle tree structure to achieve the functionality of a centralized service without the accessibility problems.
2Ease of operation
If multiple independent signers are used to enable accessibility, then ease of operation is improved, but system complexity increases
Solution Approach 1:
The patent introduces a provisioning server as an intermediary that manages the complexity of key generation and distribution. The provisioning server generates the initial keys and distributes them to multiple signers, automating the complex key management process. This intermediary handles the computational complexity while presenting a simple interface to users who can access any signer independently.
Solution Approach 2:
The patent changes the parameter structure by using a Merkle tree to organize multiple private keys under a single common public key. This parameter transformation allows the system to manage multiple signers efficiently, where the common public key serves as a unified identifier and the Merkle tree structure provides a systematic way to manage key relationships without increasing operational complexity.
3Ease of operation
If a single common public key is used for multiple signers, then ease of verification is improved, but key generation complexity increases
Solution Approach 1:
The patent applies preliminary action by having the provisioning server generate the common public key and Merkle tree structure before distributing keys to multiple signers. This pre-computation of the key hierarchy simplifies subsequent operations, as signers only need to use their pre-configured local keys without needing to understand or compute the complex relationships between multiple public keys.
Solution Approach 2:
The patent uses copying by having the provisioning server create and distribute copies of the common public key and Merkle tree path to each signer. This allows each signer to independently verify messages using identical verification data, simplifying the verification process while the server handles the complexity of generating these copied verification materials.
Data Source
AI summary
This document describes techniques and apparatuses directed at stateful hash-based signing with a single public key and multiple independent signers. Upon obtaining a Leighton-Micali signature (LMS) randomized parameter, a provisioning server may share the LMS randomized parameter among multiple signers. Next, the provisioning server may associate a unique, starting leaf index number to each signer and notify each of the signers. The signers may then create a random SEED for Leighton-Micali one-time signature (LM-OTS) signatures and generate local LM-OTS and LMS public keys. After generating the local public keys, the signers may share local LMS public keys with the provisioning server. Upon receipt of the local LMS public keys, the provisioning server may then order the local LMS public keys and generate a common LMS public key. The provisioning server can then provision the ordered list, the common LMS public key, and a Merkle tree path to each of the signers.