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Cryptanalysis of RSA Factorization - Library(ISI Kolkata) - Indian ...

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5 Reconstruction <strong>of</strong> Primes given few <strong>of</strong> its Bits 75<br />

5.1 LSB Case: Combinatorial Analysis <strong>of</strong> Existing Work . . . . . . . . 76<br />

5.1.1 The Reconstruction Algorithm . . . . . . . . . . . . . . . . . 76<br />

5.1.2 Growth <strong>of</strong> the Search Tree . . . . . . . . . . . . . . . . . . . 78<br />

5.1.3 Known Prime Bits: Complementary Sets for p,q . . . . . . . 81<br />

5.1.4 Known Prime Bits: Distributed at Random . . . . . . . . . 82<br />

5.1.5 Known Prime Bits: Distributed in a Pattern . . . . . . . . . 83<br />

5.2 LSB Case: Lattice Based Technique . . . . . . . . . . . . . . . . . . 85<br />

5.3 MSB Case: Our Method and its Analysis . . . . . . . . . . . . . . . 87<br />

5.3.1 The Reconstruction Idea . . . . . . . . . . . . . . . . . . . . 87<br />

5.3.2 The Reconstruction Algorithm . . . . . . . . . . . . . . . . . 88<br />

5.3.3 Analysis <strong>of</strong> the Reconstruction Algorithm . . . . . . . . . . 89<br />

5.3.4 Experimental Results . . . . . . . . . . . . . . . . . . . . . . 93<br />

5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94<br />

6 Implicit <strong>Factorization</strong> 95<br />

6.1 Implicit Factoring <strong>of</strong> Two Large Integers . . . . . . . . . . . . . . . 96<br />

6.1.1 The General Result . . . . . . . . . . . . . . . . . . . . . . . 96<br />

6.1.2 The MSB Case . . . . . . . . . . . . . . . . . . . . . . . . . 99<br />

6.1.3 The LSB Case . . . . . . . . . . . . . . . . . . . . . . . . . . 99<br />

6.1.4 Implicit <strong>Factorization</strong> problem when k = 3 . . . . . . . . . . 104<br />

6.2 Two Primes with Shared Contiguous Portion <strong>of</strong> Bits at the Middle . 107<br />

6.3 Exposing a Few MSBs <strong>of</strong> One Prime . . . . . . . . . . . . . . . . . 111<br />

6.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114<br />

7 Approximate Integer Common Divisor Problem 115<br />

7.1 Finding q −1 mod p ≡ <strong>Factorization</strong> <strong>of</strong> N . . . . . . . . . . . . . . . 116<br />

7.2 Finding Smooth Integers in a Short Interval . . . . . . . . . . . . . 118<br />

7.3 Extension <strong>of</strong> Approximate Common Divisor Problem . . . . . . . . 120<br />

ix

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