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SUMMARY:Cryptography and Algorithmic Randomness - Tadaki\, K (Chuo Univers
 ity)
DTSTART:20120706T090000Z
DTEND:20120706T093000Z
UID:TALK38883@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:In modern cryptography\, the random oracle model is widely use
 d as an imaginary framework in which the security of a cryptographic schem
 e is discussed. In the random oracle model\, the cryptographic hash functi
 on used in a cryptographic scheme is formulated as a random variable unifo
 rmly distributed over all possibility of the function\, called the random 
 oracle\, and the legitimate users and the adversary against the scheme are
  modeled so as to get the values of the hash function not by evaluating it
  in their own but by querying the random oracle. Since the random oracle i
 s an imaginary object\, even if the security of a cryptographic scheme is 
 proved in the random oracle model\, the random oracle has to be instantiat
 ed using a concrete cryptographic hash function such as the SHA hash funct
 ions if we want to use the scheme in the real world. However\, it is not c
 lear how much the instantiation can maintain the security originally prove
 d in the random oracle model\, nor is it clear w hether the random oracle 
 can be instantiated somehow while keeping the original security. In the pr
 esent talk we investigate this problem using concepts and methods of algor
 ithmic randomness. Our results use the general form of definitions of secu
 rity notions for cryptographic schemes\, and depend neither on specific sc
 hemes nor on specific security notions. \n\n
LOCATION:Seminar Room 1\, Newton Institute
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