RPMB is a security feature designed to protect data stored in non-volatile memory devices, such as eMMC storage. It ensures that data written to the device is not tampered with or altered during transmission. RPMB achieves this by maintaining a sequence number, which increments with each write operation, and a message authentication code (MAC) to verify the integrity of the data. This prevents replay attacks, where an attacker intercepts and retransmits old data, thereby compromising the system's security.