Pre-generated Session Keys for Contactless Payment Security
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Solution Overview
Problem
The security of cryptographic keys stored on mobile devices for contactless payment transactions is compromised if the device is lost or stolen, as they are not protected by a Secure Element, making them vulnerable to brute force attacks and protocol interception.
Innovation Solution
Generating a plurality of session cryptographic keys from a master key and transaction counter values, encrypting them, and deleting the master key after storage, ensuring that even if an attacker intercepts transaction data and cryptograms, neither the session nor master key can be obtained from the user terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cryptographic keys are stored on mobile devices for contactless payment transactions, then payment convenience is improved, but security is worsened because the device is vulnerable to brute force attacks and protocol interception without a Secure Element
Solution Approach 1:
The system pre-generates multiple session cryptographic keys before transactions occur. These keys are created in advance and stored in the mobile device, allowing the device to perform contactless payments without needing to generate keys during transactions. This preliminary preparation enables convenient contactless payments while maintaining security through pre-established cryptographic credentials.
Solution Approach 2:
The invention changes the state of cryptographic keys from a single static key to multiple dynamic session keys. By generating a plurality of session cryptographic keys with different validity periods and scopes, the system transforms the key management approach to enhance security. Each session key can be independently compromised without affecting others, and keys can be rotated based on transaction counters or time parameters.
2Productivity
If session cryptographic keys are pre-generated and stored on the device, then transaction speed is improved, but security is worsened because the keys remain vulnerable if the device is compromised
Solution Approach 1:
The system divides the single long-term cryptographic key into multiple short-lived session keys, each with specific validity parameters such as transaction counters, time windows, or merchant-specific scopes. This transformation allows the device to use pre-generated keys for fast transactions while limiting the impact of any single key compromise. The session keys are structured with embedded validity parameters that automatically restrict their use.
Solution Approach 2:
The cryptographic key material is segmented into multiple separate session keys rather than using one master key for all transactions. Each session key is a distinct cryptographic credential that can be independently managed, used, and revoked. This segmentation ensures that compromise of one session key does not expose other session keys or the device's overall security.
3Adaptability or versatility
If the master cryptographic key is retained on the device for key generation, then key management flexibility is improved, but security is worsened because the master key becomes a target for attackers
Solution Approach 1:
The master cryptographic key is extracted from the mobile device and stored in a secure remote location such as a secure element or remote server. The device retains only the generated session cryptographic keys needed for transactions. This extraction removes the high-value target from the device while maintaining the ability to generate new session keys through secure key management infrastructure.
Solution Approach 2:
The system replaces the need for a persistent master key on the device with multiple disposable session keys. Each session key is designed to be used once or for a limited scope, then discarded. These short-lived keys are regenerated as needed from the remote master key, eliminating the security risk of storing a permanent master key on the device while maintaining operational flexibility.
Data Source
AI summary
Methods and devices for pre-generating session keys for securing transactions are provided. A plurality of session cryptographic keys are generated from a master cryptographic key and a respective plurality of possible values of a transaction counter. The session cryptographic keys are encrypted to provide a plurality of encrypted session cryptographic keys, which are stored in the user terminal. The master cryptographic key is deleted from the user terminal after the session keys are generated. To secure a transaction, a cryptogram is generated based on one of the encrypted session cryptographic keys and transaction data for the transaction, and the cryptogram is transmitted to a transaction terminal. The transaction counter is updated, and the encrypted session cryptographic key is deleted from the user terminal.