To store or not to store a key that is the question! Pim Tuyls - - PowerPoint PPT Presentation

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To store or not to store a key that is the question! Pim Tuyls Philips Corporate Technologies, Business Unit Intrinsic-ID 28 May 2008 Corporate Venturing White Box Cryptography ECRYPT 2008 2 Security & Cryptography Is more and more

SLIDE 1

Pim Tuyls Philips Corporate Technologies, Business Unit Intrinsic-ID

28 May 2008

To store or not to store a key that is the question!

SLIDE 2

2 ECRYPT 2008

Corporate Venturing

White Box Cryptography

SLIDE 3

3 ECRYPT 2008

Security & Cryptography

Is more and more important in various applications and industries

SLIDE 4

4 ECRYPT 2008

Black-Box Crypto Model

M EK(M) E(.)

Assumption: Key is stored securely

SLIDE 5

5 ECRYPT 2008

Zoo of Options for Secure Key Storage

Poly Fuse Laser Fuse E - Fuse EEPROM Flash EPROM Anti Fuse

So what is the problem?

Battery Backed RAM

SLIDE 6

6 ECRYPT 2008

Secret Key: 001011101011

Physical Attacks

Micro Probes Focused Ion Beam

The problem: Physical Attacks

SLIDE 7

7 ECRYPT 2008

Why storing a key? Why not generating a key?

1. Do not store a key in digital form in a device
2. Generate the key only when needed
3. Delete the key

SLIDE 8

8 ECRYPT 2008

Physical Unclonable Function (PUF)

Physical Unclonable Function (PUF): Inherently unclonable physical structure (due to process variations) satisfying:

Easy to evaluate: Challenges-Responses
Inherently tamper evident
Inseparably bound to the object
Manufacturer not-reproducible

SLIDE 9

9 ECRYPT 2008

Cryptographic Analogy of PUFs: Hard Problem

Easy

Making a Random PUF Making/Modeling a Specific PUF

Difficult

SLIDE 10

10 ECRYPT 2008

Examples of PUFs

IC with SRAM PUF

M1 M1 M1 M1 M2 M2 M2 M2 M3 M3 M3 M3 M4 M4 M4 M4 M5 M5 M5 M5 transistors transistors transistors transistors passivation passivation passivation passivation

Coating Coating Coating Coating-

PUF PUF PUF

On chip demo

IC with Coating PUF

Intrinsic Identifier

Optical PUF

SLIDE 11

11 ECRYPT 2008

5 10 15 20 25 30 0.02 0.04 0.06 0.08 0.1 0.12

Measurement Nr. Error Fraction

E rrors in M RA M startup values over tem perature T=-20oC T=0oC T= 20oC T=40oC T= 60oC T=80oC | | | | | | |

Industrialisation of S-RAM PUFs

Ageing test up 15 years, supply voltage variation tests were performed: stable!

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12 ECRYPT 2008

Key Extraction from a PUF

Helper Data Algorithm Required

– Error Correction – Randomness Extraction

Enrollment

– Creates Helper Data – Creates Key

Key Reconstruction

– Uses helper data – Reconstructs key PUF HD ECC

SLIDE 13

13 ECRYPT 2008

Secret Key Algorithm

Storage Mechanism

Interface OTP / MTP Key2HD PUF HD2Key

1011010 1010101 1010 1011010 1010101 1010

SLIDE 14

14 ECRYPT 2008

Advantages

Very low cost, less area than other technologies
Compatible with semi-conductor processes
Key is not present when the device is not running
No issues with Shelf live
No additional components with life-time issues

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15 ECRYPT 2008

Other Applications

Prevention of Counterfeiting of Goods

– IP Protection (e.g. on FPGA)

Product Metering

– Prevention of overbuilding

OEM Intrinsic ID

measurement

Activation code IP 100% Reporting Activation Service IP Owner

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ECRYPT 2008