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Building Blocks - SBox Constraint Example

Output Values Oracle

3. Building Blocks

Output

Registry-Node

A New Framework for Side Channel Cryptanalysis

Input Values Oracle

SBox

Compute-Node

Input

Registry-Node

=

Questions?

Sources available at

www.OfirWeisse.com

OfirWeisse@Gmail.com

Registry

Records

Building Blocks - XOR Constraint Example

Yossef Oren

Columbia University, USA

2. Probabilistic Toolbox

Probabilistic Methodology

Ofir Weisse

Observer 1

Observer 2

Tel-Aviv University, Israel

Observer 2's opinion

Observer 1's opinion

1. Problem Domain

Avishai Wool

Requirements

Offline Phase: Profiling

Device Under Test

Tel-Aviv University, Israel

Evolution Of Entropy

Profiles

On-Line Phase

Device Under Attack

Measure Device

5. DPA Results

Results on DPA v4 Data Set

9 seconds running time per

power trace (median)

2 power traces required to yield correct key

as rank 1 (at 79.6% success)

4. Cracking AES

Compile Equations Set

Source code available online

Constraint Graph for AES (first round)

Mix Columns

Single Input Computations

2,13

XOR of 4 - Take II

AddKey

SubBytes

Candidate Key Quarters

Finding The Key

7,8

2,7

7,8

2

~500 X

2,7

7,8

2,7

2

~500 X

XTimes = multiply by 2

XOR of 4 - Take I

Profiles

(From offline phase)

13,8

Solve equations and find the key

2

500

Correct key quarter is mostly

among the top 10

~500

Pruning by conflated probability

Strengthen points of agreement

2

500

256 X

2

500

2

500

Prefer accurate observation (with low variance)

over less accurate (with high variance)

Can intersect candidates from

2 runs

=

2

~500 X

2

~500 X

x

Weaken points of disagreement

Eliminate points deemed impossible by an observer

to next compute

node

=

Conflation:

x

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