Contactless Session Key Exchange Without Shared Secrets
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Solution Overview
Problem
Existing solutions for secure communication in contactless RFID systems, such as those used in 'tap and go' transactions, face challenges in ensuring confidentiality without prior knowledge sharing, particularly in devices like terminals and readers that lack a security module, and must adhere to strict transaction duration constraints.
Innovation Solution
A method using asymmetric and symmetric encryption algorithms, specifically 'RSA for paranoid' and DES, respectively, to establish secure communication and authentication without shared secrecy, involving random number generation, cryptographic certificates, and modular exponentiation, ensuring secure key exchange within the constraints of contactless transactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing solutions based on joint knowledge of secrecy are used, then security can be ensured in devices with security modules, but it becomes complex to guarantee confidentiality in devices without security modules and requires embedding security modules in all devices
Solution Approach 1:
The patent applies asymmetry by using asymmetric cryptography (public key infrastructure) where the device holds a private key and the server holds a public key. This eliminates the need for symmetric key distribution and security modules in the device, as the server alone manages the cryptographic keys. The asymmetric key pair enables secure communication without requiring the device to have embedded security hardware.
Solution Approach 2:
The patent introduces a server as an intermediary that manages the cryptographic keys and authentication process. The server acts as a mediator between the device and the secure communication channel, handling key generation, storage, and verification. This intermediary approach centralizes security management, eliminating the need for security modules in endpoint devices.
2Reliability
If secure communication establishment follows existing methods, then security can be maintained, but the transaction duration exceeds the 150ms constraint required for tap and go applications
Solution Approach 1:
The patent applies preliminary action by pre-generating and storing asymmetric key pairs in the device before the transaction occurs. The private key is stored in the device's secure element, and the corresponding public key is registered with the server in advance. During the actual transaction, no key generation or exchange is needed, only fast authentication operations, enabling completion within 150ms.
Solution Approach 2:
The patent extracts the computationally intensive key generation and management operations from the transaction flow, performing them in advance. The complex cryptographic operations are separated from the time-critical authentication phase, allowing the transaction to proceed with only lightweight verification steps that meet the 150ms constraint.
3Reliability
If security modules are embedded in all devices to ensure confidentiality, then security is improved, but the cost increases and devices without security modules cannot guarantee confidentiality
Solution Approach 1:
The server acts as an intermediary that centralizes security module functionality. Instead of embedding security modules in every device, the server provides cryptographic services to multiple devices. The device's simple secure element stores only the private key, while the server handles key management, certificate validation, and session key generation, eliminating the need for expensive security modules in each device.
Solution Approach 2:
The server provides universal cryptographic services to multiple devices, making the security infrastructure reusable and cost-effective. A single server with robust security capabilities serves many devices, each with minimal security requirements. This multi-functional approach replaces the need for individual security modules in each device with a shared security service.
Data Source
AI summary
The invention relates to a method for generating a session key between two communicating electronic devices not requiring any prerecorded information in one of the two devices and enabling the authentication of one of said devices. The method uses a close collaboration between a symmetrical algorithm and an asymmetrical algorithm.