Secret-Key Generation from Physics Onur G unl u onur.gunlu@tum.de - - PowerPoint PPT Presentation

Institute for Communications Engineering Technische Universit¨ at M¨ unchen

Secret-Key Generation from Physics

Onur G¨ unl¨ u

• nur.gunlu@tum.de

Supervisor: Gerhard Kramer

January, 2015 - SPCodingSchool, Campinas - Brazil

Onur G¨ unl¨ u — Secrecy via Physical Unclonable Functions (PUFs) 1/4

Institute for Communications Engineering Technische Universit¨ at M¨ unchen

Problem Definition

Secret-key generation from Physical Unclonable Functions:

They are cheap and safe alternatives to Non-Volatile Memory for storing the secret key. The source of randomness (i.e., unique fingerprints of Ring Oscillators [ROs] or SRAMs) is used to extract the key. Transmitter = Receiver = PUF. To reconstruct the key, side information (i.e., helper data) is stored to correct errors in the regenerated bits. The reconstructed secret key can be used in a one-time pad scenario to provide unconditional security or authentication.

Onur G¨ unl¨ u — Secrecy via Physical Unclonable Functions (PUFs) 2/4

Institute for Communications Engineering Technische Universit¨ at M¨ unchen

Discrete Cosine Transform (DCT)-based RO PUFs

RO Array NxM

f

f1 f

Type IV NxM - DCT

C

c512 Quantization

q

q

Gray(q ,L ) Gray Coding

Concatenation

Q B

512 c1

1 qK K K

Gray(q ,L )

1 1

Figure 1: Secret-key Generation via DCT-based RO PUFs

Main Benefits High uniqueness in RO PUF outputs by eliminating systematic and spatial variations; A trade-off between the number of bits generated and error probability of PUF outputs; Increased reliability by decreasing sensitivity to temperature and voltage variations.

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Institute for Communications Engineering Technische Universit¨ at M¨ unchen

Reliability of the DCT Coefficients

Define the average bit-error probability per extracted bit as the distortion measure for each DCT coefficient. Extract L bits from a coefficient if the distortion D(L) is less than the predefined error probability pb.

2 4 6 8 10 12 0.02 0.04 0.06 0.08 0.1 0.12 Number of Bits L Mean Number of Errors D(L) pb = 8/128

Figure 2: Average bit-error probability per extracted bit

Thank you!

Onur G¨ unl¨ u — Secrecy via Physical Unclonable Functions (PUFs) 4/4