Incorrect Selection of Fuse Values

Hardware fuses are commonly used for one-time programmable (OTP) memory to store secrets or security settings. By design, an unblown fuse reads as a logic 0, while blowing it changes the reading to a logic 1. The security flaw arises when the system's firmware or logic gates are configured with negative logic, interpreting a blown fuse (logic 1) as a command to disable security protections. Since fuses are irreversible, an attacker's single action of blowing the targeted fuse can permanently lock the device into a compromised state. This highlights a critical design error: the secure condition must be represented by the blown (logic 1) state, not the unblown state, to prevent an attacker from easily overriding security by manipulating the fuse.