Tropic Square TROPIC01 MAC-and-Destroy PIN Verification is a hardware-based PIN authentication mechanism implemented on the TROPIC01 secure chip. It replaces conventional PIN verification approaches that rely on stored hashes and software retry counters with a physically irreversible hardware operation. How it works: - Each PIN attempt triggers a two-step hardware operation using a KMAC (Keccak-based Message Authentication Code) engine - The first KMAC core generates a hardware fingerprint unique to the chip and writes it into a dedicated memory slot, overwriting and physically erasing the previous slot content - A second KMAC core combines the old slot value with the new one; if the relationship matches the expected result, the PIN is accepted - If verification fails, the slot is permanently consumed and cannot be retried, replayed, or reset - The entire read-compute-write-verify sequence is indivisible; skipping any step breaks verification entirely Key security properties: - No stored hash exists to extract - No retry counter exists to reset or glitch - No branching comparison logic exists for fault injection attacks - Each attempt permanently changes physical hardware state, making rollback attacks (voltage manipulation, memory dumps, state restoration) ineffective - PIN values are mixed at two separate cryptographic stages using chip-unique PUF (Physically Unclonable Function) keys, providing protection against malicious chip manufacturers or compromised provisioning pipelines - Supports multiple independent PINs protecting the same secret, each with separate verification data and encrypted material - Includes a Wiping PIN that appears as a normal PIN check but triggers irreversible memory self-destruction when entered, intended for duress scenarios The TROPIC01 chip uses an open, auditable architecture intended for applications such as hardware wallets, IoT devices, and critical infrastructure.