Ephemeral Cryptogram Generation via Server-Side Key Derivation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The security of user devices in payment transactions is compromised due to the risk of cryptogram interception and the potential untrustworthiness of devices lacking secure elements or hardware protection, making it challenging to conduct secure transactions without persistently storing sensitive data.
Innovation Solution
A method where user devices and server computers mutually authenticate to generate ephemeral key pairs, derive shared secrets, and use these to encrypt and decrypt data, allowing for secure cryptogram generation and transaction processing without storing encryption keys on the device, with key derivation parameters unique to each device to prevent mass attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cryptogram generation keys are stored persistently on user devices, then transaction authentication is enabled, but security is compromised due to potential device compromise and key interception
Solution Approach 1:
The system performs preliminary key derivation and cryptogram generation before the actual transaction occurs. The server derives cryptogram keys in advance using device-specific parameters, and the user device generates cryptograms beforehand using these keys. This preliminary action ensures that no persistent secret keys are stored on the device, eliminating the risk of key interception while maintaining transaction security.
Solution Approach 2:
A server acts as an intermediary between the user device and the transaction system. The server stores device-specific parameters and performs key derivation, mediating the security-sensitive operations. This intermediary approach allows the user device to operate without storing secret keys, while the server maintains secure records for authentication purposes.
2Reliability
If secure elements or hardware protection are implemented, then key storage security is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts the secret key storage function from the user device and relocates it to the server. Device-specific parameters are stored on the server rather than the user device, eliminating the need for secure elements or hardware protection on the user device. This extraction resolves the contradiction by maintaining security through server-side storage while reducing device complexity.
Solution Approach 2:
The system uses device-specific parameters (such as device identifiers or characteristics) that naturally exist on each user device to derive unique cryptogram keys. Each device serves itself by providing these parameters, which the server then uses to generate device-specific keys without requiring additional security hardware on the device.
3Productivity
If static cryptogram generation keys are used, then transaction processing is simplified, but security is weakened due to potential mass attacks
Solution Approach 1:
The system implements local quality by deriving unique cryptogram keys for each individual device based on device-specific parameters. Instead of using a single static key for all devices, each device receives a customized key derived from its unique characteristics. This per-device customization prevents mass attacks while maintaining efficient transaction processing through automated key derivation.
Solution Approach 2:
The system changes the parameter space by using device-specific parameters (such as device identifiers, hardware characteristics, or provisioning data) as inputs to key derivation functions. This parameter variation ensures that each device has a unique cryptogram key without requiring manual configuration or complex key management, maintaining processing efficiency while enhancing security against mass attacks.
Data Source
AI summary
A computer-implemented method performed by a user device is provided. The computer-implemented method includes receiving a message including an encrypted credential from a server computer; determining a response shared secret using a private key and a server public key; decrypting the encrypted credential using the response shared secret to determine a credential; obtaining a key derivation parameter from the credential; determining a first cryptogram key using the key derivation parameter; generating a first cryptogram using the first cryptogram key; and sending the first cryptogram to a second computer.