Key Ladder Generating Device Public Key
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Solution Overview
Problem
Existing key ladder systems using symmetric keys are vulnerable as a compromised server with a database of device symmetric keys can expose all device secrets, and devices with limited secure storage face challenges in managing multiple public keys for secure communications.
Innovation Solution
A method and system for generating a key ladder that uses asymmetric keys, where a device generates a chip-unique application public key from a private key, allowing secure communication without storing multiple public keys, and computes a shared symmetric key using device public and private keys, reducing storage requirements and enhancing security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If symmetric keys are used in key ladders, then secure communication between devices is achieved, but compromise of a server with a database of device symmetric keys exposes all device secrets
Solution Approach 1:
The patent applies asymmetry by transitioning from symmetric key ladders to asymmetric key ladders where public keys are stored on the server instead of private keys. This creates a fundamental asymmetry in key management: public keys can be freely distributed and stored, while private keys remain exclusively on devices. This resolves the vulnerability because even if the server is compromised, attackers only obtain public keys which cannot be used to derive private keys or compromise device security.
Solution Approach 2:
The patent extracts the secret key material from the server entirely. Instead of storing device private keys or symmetric keys on the server, the system only stores public keys which contain no secret information. This extraction eliminates the risk of server compromise exposing device secrets, as the server no longer holds any extractable secret material that could compromise device security.
2Reliability
If devices store multiple public keys for secure communications, then security is enhanced, but devices with limited secure storage face challenges in managing these keys
Solution Approach 1:
The patent merges multiple public key storage requirements into a single unified public key stored on the server. Instead of each device storing multiple public keys for different communication partners, the system combines all public key management into the server's database. Devices only need to store their own private key and can retrieve any public key from the server, dramatically reducing on-device storage requirements while maintaining security.
Solution Approach 2:
The server's public key database serves multiple functions: it stores public keys for authentication, enables key distribution for multiple communication partners, and provides a centralized repository that all devices can access. This universal solution eliminates the need for each device to independently manage multiple public keys, reducing storage burden while maintaining comprehensive security capabilities.
Data Source
AI summary
A method is provided for generating a key ladder for securely communicating between a first device and a second device using a first device symmetric key and a chip-unique private key. The method includes generating a second processor-specific first device symmetric key from a first processor-specific first device symmetric key and a first identifier (CPU_ID), generating a chip-unique first device application private key (CUAPrK) from a second identifier and the second processor-specific first device symmetric key, generating a chip-unique first device application public key (CUAPuK) from the chip-unique first device application private key (CUAPrK), and transmitting the chip-unique first device application public key (CUAPuK) and an identifier of the processor to the second device.