1. Purpose and scope
Every customer design reaches the device as a bitstream: a file, written by the vendor's software, that sets every configuration cell in the fabric and every setting of the hard IP. The configuration logic loads it, checks it and starts the design. If configuration is unreliable, nothing else about the device matters; if it is insecure, a customer's design can be copied, altered or replaced in the field. This stage designs both.
The configuration side covers the configuration memory and how it is organised into frames or similar addressable units, the configuration controller and its interfaces, such as external flash, a host processor or the test access port, the power-up and start-up sequence, the bitstream format, partial reconfiguration where the family offers it, readback, and detection and correction of upsets in the configuration memory during operation.
The security side covers encryption of the bitstream so the design cannot be read from the external memory, authentication so the device loads only bitstreams signed by the owner, key storage in one-time programmable fuses, battery-backed memory or a physically unclonable function, protection against rollback to older bitstreams, disabling of readback and debug access, resistance to side-channel attacks, and the response when tampering is detected, such as clearing keys and the configuration.
Security features are designed against a threat model, not a feature list. The threat model names who might attack a deployed device, what they want, what access they have and which features stop them, and every threat is either covered by a feature or recorded as an accepted risk.
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