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SAT Based Attacks on SipHash - Department of Computer Science

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iv<br />

C<strong>on</strong>tents<br />

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<br />

iii<br />

1 Introducti<strong>on</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1<br />

1.1 Message Authenticati<strong>on</strong> Code . . . . . . . . . . . . . . . . . . . . . . . . 1<br />

1.1.1 <strong>SipHash</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2<br />

1.2 Boolean Satisfiability Problem . . . . . . . . . . . . . . . . . . . . . . . . 4<br />

1.3 <str<strong>on</strong>g>SAT</str<strong>on</strong>g> solver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4<br />

2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6<br />

2.1 Building the CNF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6<br />

2.1.1 CNF for AND . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7<br />

2.1.2 CNF for OR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7<br />

2.1.3 CNF for XOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8<br />

2.1.4 CNF for ADD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9<br />

2.1.5 Rotati<strong>on</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10<br />

2.2 C<strong>on</strong>verting <strong>SipHash</strong>-c,d to CNF . . . . . . . . . . . . . . . . . . . . . . . 11<br />

2.2.1 Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11<br />

2.2.2 Intermediate variables . . . . . . . . . . . . . . . . . . . . . . . . 12<br />

2.2.3 Initializati<strong>on</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12<br />

2.2.4 SipRound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12<br />

2.2.5 Variable parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 13<br />

2.3 Data Collected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15<br />

3 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16<br />

3.1 <strong>SipHash</strong>-c,d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16<br />

3.1.1 <strong>SipHash</strong>-1,x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17<br />

3.1.2 <strong>SipHash</strong>-x,1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19<br />

3.1.3 <strong>SipHash</strong>-1,0 With More Missing Key Bits . . . . . . . . . . . . . . 19

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