Electronic Design

The Key To Security

The proliferation of the Internet, mobile applications, and networked devices has simplified the exchange of digital content between many of today’s consumer electronics devices, such as Apple’s recently introduced iPhone, PCs, set-top boxes, and DVD players. But these sharing capabilities also have increased the piracy music, movies, and other digital content.

While digital content producers embrace the proliferation of products, they also need to protect their revenue streams by taking measures to prevent theft and unauthorized redistribution. Digital rights management (DRM) is a content protection scheme that effectively deters piracy with a cryptosystem that encrypts digital content and uses encryption keys to decrypt the content.

In 1883, cryptographer Auguste Kerckhoffs stated in his Kerckhoffs’ Principle that it should be assumed an attacker knows the details of the cryptosystem. Thus, the security of the cryptosystem should be based on the security of the encryption key, not the algorithm. Therefore, a successful attack should be assumed. The security of the system then relies on how well the encryption key is protected along with how well that system recovers from a successful attack.

As Kerckhoffs stated, the security of the cryptosystem is based on the security of the encryption key, so it’s critical for the key to be well protected and not subject to exposure. But if the encryption key is somehow compromised, it must be able to be updated for the encryption system to recover from the attack. If the encryption key were static and consequently compromised, the system wouldn’t be able to recover.

The figure depicts an unsecured environment and a secured environment. In the unsecured environment on the left, a discrete EEPROM is used to store the encryption key. When the system-on-a-chip (SoC) accesses the encryption key from the EEPROM, the key is exposed and can be probed. As for the secured environment on the right, the key is securely stored in embedded nonvolatile memory directly on the SoC, represented by the NOVeA block. So, it isn’t vulnerable to probing.

This approach addresses the first issue of security, namely ensuring the security of the encryption key. To address the second level of security, specifically the ability to update the encryption key if it is compromised, the chosen embedded nonvolatile memory should be a multitime programmable (MTP) memory.

In addition to ensuring the security of the encryption key, the chosen embedded nonvolatile memory solution must be cost-effective to address the cost-sensitive nature of the consumer space. To minimize costs, the chosen embedded nonvolatile memory should require no additional masking, process steps, or process modifications. And, it should be able to be manufactured on a standard CMOS logic process.

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