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Unformatted text preview: MIT 6.443J / 8.371J / 18.409 / MAS.865 Quantum Information Science April 27, 2006 Unconditional Security of QKD 1. Cryptography 2. Quantum Key Distribution: BB84 3. EPR Protocol 4. CSS Code Protocol 5. Secure BB84 1 Crytography secret comm. PKC auth DSS In the Vernam Cipher (onetime pad), Alice and Bob share a secret key k . A key k B msg m m' m'+k=m m+k Eve has m + k , but I ( m + k, m ) = H ( m + k ) H ( m + k/m ) = H ( m + k ) H ( k ) = 0 The key k is called a pad. It is referred to as onetime because k cant be reused. 1 Distribution of k security criterion I (Eve , key) = 2 l where resources required poly( l ). 2 Quantum Key Distribution: BB84 A rand b in {0,1} rand b' in {0,1} a' Bob H H channel a = ,   1 = , Keep all bits for which b = b . A and B hash obtain key k . Thm. Info gain disturbance. In any attempt to distinguish nonorthogonal states and  , information gain is only possible at the expense of disturbing the states.  Proof. WLOG assume   u   v   u...
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This note was uploaded on 02/07/2012 for the course MAS 6.443J taught by Professor Petershor during the Spring '06 term at MIT.
 Spring '06
 PeterShor

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