White-Box Cryptographic Relay Attack Defense
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Solution Overview
Problem
In white-box cryptographic implementations, relay attacks remain a challenge despite key hiding, as attackers can misuse the cryptographic functionality, and existing methods to make relay attacks more difficult are insufficient.
Innovation Solution
The method involves adding dummy computations to cryptographic operations on mobile devices, ensuring they complete just in time before a reader's time-out, making it difficult for attackers to successfully perform relay attacks by extending the execution time through linear encodings and their inverses, thereby limiting the window for a successful relay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dummy computations are added to extend cryptographic operation time, then relay attack difficulty increases, but execution time increases
Solution Approach 1:
The patent converts the harmful factor of time (which attackers can exploit for relay attacks) into a beneficial security feature by adding dummy computations that consume time. The time extension, which initially seems to worsen performance, actually creates a time window mismatch that prevents relay attacks from succeeding, as the extended execution time causes timing inconsistencies between challenge issuance and response verification.
2Reliability
If dummy computations are added to cryptographic operation, then relay attack window is reduced, but computational complexity increases
Solution Approach 1:
The patent introduces dummy computations as an intermediary element between the actual cryptographic operation and the attacker's relay attack mechanism. These dummy computations act as a mediator that consumes time and creates timing delays, preventing the attacker from successfully coordinating the relay attack without requiring changes to the core cryptographic algorithm itself.
3Reliability
If execution time is extended to consume available time window, then attacker's relay attack success rate decreases, but time-out margin decreases
Solution Approach 1:
The patent changes the time parameter of the cryptographic operation by adding dummy computations that extend the execution time. This parameter change transforms the operation to consume nearly the entire available time window, leaving minimal margin for relay attacks. The timing parameter becomes a security control mechanism, where the extended execution time creates a mismatch between challenge issuance and response verification that prevents successful relay attacks.
Data Source
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AI summary
A method is provided for performing a cryptographic operation in a white-box implementation on a mobile device. The cryptographic operation is performed in the mobile device for a response to a challenge from a mobile device reader. The mobile device reader includes a time-out period within which the cryptographic operation must be completed by the mobile device. In accordance with an embodiment, a first-time period to complete the cryptographic operation on the mobile device is determined. A predetermined number of dummy computations are added to the cryptographic operation to increase the first-time period to a second-time period. The second-time period is only slightly less than the time-out period by a predetermined safety value to make it less likely a relay attack with be successful.