Secure Element OTP Access Control Against Chipset Cloning
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Solution Overview
Problem
Existing chipsets with one-time-programmable (OTP) areas for secret data storage face risks of unauthorized access and cloning due to unprogrammed states, leading to potential fraudulent use and loss of functionality for companies relying on conditional access systems.
Innovation Solution
A method and electronic device that generate and store an initialization value in the OTP area if no secret data is present, using a cryptographic key and algorithm to decrypt and verify the integrity of secret data, ensuring only authorized entities can access and program the OTP area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the OTP area is kept accessible and unprogrammed, then the chipset can be recovered and reprogrammed by authorized entities, but unauthorized persons can clone the chipset by copying secret data
Solution Approach 1:
The system performs preliminary actions by generating an initialization value and storing it in the OTP area during the first boot if no secret data is present. This preliminary setup creates a cryptographic barrier that prevents subsequent unauthorized programming while allowing authorized entities with the correct key to reprogram the device.
Solution Approach 2:
The initialization value acts as an intermediary element between the unprogrammed OTP area and the secret data. It serves as a cryptographic mediator that must be processed with the correct key before any secret data can be loaded, thereby controlling access without preventing reprogrammability.
2Object-affected harmful factors
If the OTP area is burned to prevent unauthorized access, then cloning is prevented, but the chipset cannot be reprogrammed by authorized entities
Solution Approach 1:
Instead of immediately burning the OTP area, the system performs a preliminary check during first boot to determine whether secret data should be loaded. Only if the device is confirmed to be used for purposes other than conditional access does the system burn the OTP area, thereby avoiding premature destruction of reprogrammability.
Solution Approach 2:
The protection mechanism is dynamic rather than static. The OTP area transitions from an accessible state to a protected state based on runtime conditions (whether secret data is loaded), allowing flexibility for authorized reprogramming while providing protection when needed.
3Ease of manufacture
If secret data is stored in plain text in black-boxes, then manufacturing is simplified, but security is compromised as manufacturers have full access to secrets
Solution Approach 1:
The secret data is extracted from the plain text storage in black-boxes and transformed into encrypted form stored in the OTP area. The initialization value and cryptographic key mechanism separate the security-critical secret data from accessible storage, thereby improving security while maintaining manufacturing simplicity through automated encryption during programming.
Data Source
AI summary
A method for controlling access to a resource in an electronic device including a secure element with a permanent memory having an OTP area. The method includes the following steps performed first when the secure element or the electronic device boots: checking presence of at least one of a secret data and an initialization value in the permanent memory and, in a negative event, generating an initialization value and storing it into the OTP area, in a positive event, if the permanent memory includes secret data, decrypting, within the secure element, the secret data by using an algorithm using a cryptographic key and, if the permanent memory further includes an initialization value, the initialization value, and checking the integrity of the secret data by using a signature stored in the permanent memory and, on successful completion, providing access to the resource.