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cosec >students >Teaching >Winter 2007/2008 

When Stream Cipher Analysis Meets Public-Key Cryptography

Laila El Aimani (cosec - b-it)

Thursday, 6 December, 2007, 15:00 sharp (s.t), b-it 1.25 (cosec meeting room)

The talk reports on the two papers:

  1. When Stream Cipher Analysis Meets Public-Key Cryptography (by Matthieu Finiasz and Serge Vaudenay - SAC 2006)
  2. TCHo: a Hardware-Oriented Trapdoor Cipher (by Jean-Philippe Aumasson, Matthieu Finiasz, Willi Meier and Serge Vaudenay - ACISP 2007)

Inspired by fast correlation attacks on stream ciphers, we present a stream cipher-like construction for a public-key cryptosystem whose security relies on two problems: finding a low-weight multiple of a given polynomial and a Hidden Correlation problem. We obtain a weakly secure public-key cryptosystem we call TCHo (as for Trapdoor Cipher, Hardware Oriented). Using the Fujisaki-Okamoto construction, we can build an hybrid cryptosystem, TCHo, resistant against adaptive chosen ciphertext attacks.

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