Philips patents self-destructing MRAM

Magnetic Random Access Memory (MRAM) was developed by Honeywell and Motorola as a successor to flash memory. Now Philips has plans to make it hacker-proof.

Unlike conventional RAM chip technologies, data is not stored as electric charge or current flows, but by magnetic storage elements. The elements are formed from two ferromagnetic plates, each of which can hold a magnetic field, separated by a thin insulating layer. One of the two plates is a permanent magnet set to a particular polarity, the other's field will change to match that of an external field. A memory device is built from a grid of such "cells".

If, however, a hacker opens the chip, they can easily read sensitive data from the layers directly. This could be a problem if an MRAM chip is used for high-security applications, like storing passwords or cryptographic keys.

The thin-film magnets in Philips' tamper-proof chip will be wrapped in a soft metal sheet and then topped with another thin-film magnet.

While the wrapper remains intact the soft metal acts as a "keeper", gathering flux from the permanent magnet into a closed loop and keeping it away from the MRAM stack. But if someone attempts to break through the metal wrap to access the MRAM layers, the keeper becomes ineffective. Flux then breaks out and immediately erases the magnetic data stored in the MRAM chip.

The beauty of the system is that it is passive. So, disconnecting power to the chip does not keep the permanent magnet from doing its job.