QUANTUM CRYPTOGRAPHY

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					  QUANTUM
CRYPTOGRAPHY

     Matthew Suhre
                        Overview
   History of Cryptography
   Cryptography Basics
   RSA Encryption
       Algorithm
       Example
   Quantum Cryptography
       History
       Process
       Pros and Cons
       Open Air Cryptography
          Cryptography History
   Dates Back to Julius Ceaser
     Didn’t trust messanger
     Used “Shift by 3” method
            Cryptography Basics
   Cryptosystem (Cipher System) – method of
    disguising messages so that only certain people can
    read them
   Cryptography – Art of creating and using
    Cryptosystems
   Cryptanalysis – Art of breaking Cryptosystems
   Cryptography – study of Cryptography and
    Cryptosystems
             Cryptography Basics
   Symmetric Cryptosystems use the same key to
    encrypt and decrypt
       You need to send the key securely
   Asymmetric Cryptosystems use a public key to
    encrypt and a private key to decrypt
              RSA Encryption
   Invented in 1978 by Ron Rivest, Adi Shamir and
    Leonard Adleman
   Algorithm for public key encryption
        RSA Encryption Algorithm
   1. Find P and Q two large prime numbers
   2. Choose E such that: 1<E<PQ
     E does not have to be prime, but must be odd
     (P-1)(Q-1) and E must not have no prime factors in
      common
   3. Compute D such that (DE-1) is evenly
    divisible by (P-1)(Q-1)
        RSA Encyrption Algorithm
   4. Encryption function is C = (T^E) mod PQ
     C is the ciphertext (positive integer)
     T is the plaintext (positive integer)
     T must be less then the modulus PQ

   5. Decryption function is T = (C^D) mod PQ
     C is the ciphertext (positive integer)
     T is the plaintext (positive integer)
     D is the private key
Example of RSA Encryption
                 RSA Encryption
   Relying on
     No one can solve
     Would take to long to solve

   Theoretically Can be Broken
    Quantum Cryptography History
   Early 1970’s Stephen Wiesner wrote “Conjugate
    Coding”
   1979 Charles H. Bennett and Gilles Brassard
    wrote various papers on the subject
   Basis: Takes advantage of Heisenberg’s principle
    in which measuring a quantum system disturbs it
    and yields incomplete information
    Quantum Cryptography Setup
   Most widely used is the BB84 Protocol
    developed by IBM
   The sending apparatus consists of a green light-
    emitting diode, a lens, a pinhole and mirrors that
    provide a collimated beam of horizontally
    polarized light. Next, electronic devices known
    as Pockels Cells are used to change the original
    horizontal polarization to any of four standard
    polarization states under the users control
    Quantum Cryptography Setup
   The receiving apparatus contains a similar
    Pockels cell, which allows the user to choose the
    type of polarization he will measure. After the
    beam passes through hte Pockels Cell, it is split
    by a calcite prism into two perpendicularly
    polarized beams, which are directed into two
    photomultiplier tubes for the purpose of
    detecting individual photons
 Alice Sends Polarizations



Bob randomly chooses measurement



      Bob records the results



       They Check the results



      This then becomes the
      key
         Quantum Cryptography
   If someone tries to steal the signal
     Measurements are changed
     Signal is slower/weaker

     Sender/Reciever can stop
                        Pros
   Nearly Impossible to steal
   Detect if someone is listening
   “Secure”
                            Cons
   Price limits length
     Normally just for a local network about 10km
     Record set by Los Almos is 31 miles

     Longer length, signal is absorbed, noise increased

   Availability
   Compete with traditional networks
       If was a straight pipe, distance could be limitless
                  Free Space
   Being developed for longer distances
   May be possible to send from ground satellites
    to space satellites
   Longest recorded is ½ km, at Los Almos
                       Summary
   History of Cryptography
   Cryptography Basics
   RSA Encryption
       Algorithm
       Example
   Quantum Cryptography
       History
       Process
       Pros and Cons
       Open Air Cryptography
                   Bibliography
   http://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-QC.html
   http://www.qubit.org/intros/crypt.html
   http://www.faqs.org/faqs/cryptography-faq
   http://world.std.com/~franl/crypto.html
   http://www.lanl.gov/orgs/pa/science21/QuantumCrypto.html
   http://www.almaden.ibm.com/st/projects/quantum/crypto/
   http://www.quantum.univie.ac.at/research/crypto/
   http://www.rsasecurity.com/rsalabs/faq/sections.html
   http://www.sciam.com/news/122200/2.html
   http://world.std.com/~franl/crypto/rsa-guts.html

				
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