7.authen-key

7.authen-key - Entity Authentication and Key Agreement CSE...

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Entity Authentication and Key Agreement CSE 651
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Entity Authentication Problem: Alice wants to prove to Bob that she is Alice and/or vice versa. Basic idea: Alice shows that she knows some secrecy which is presumably known only to Alice (and Bob). That secrecy could be, for example: - Alice’s password or PIN - a MAC or encryption key shared by Alice and Bob, or - Alice’s RSA private key.
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: 0. Alice Bob: "I'm Alice" 1. Alice Bob: "What's your password?" 2. Alice Bob: Alice's password 3. Bob verifies the passw Protoc ord ol Is it secure against an eavesdropper?
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() : (0. Alic Alice and Bob share a secret key . ins e Bob: "I'm Alice") 1. Alice Bob: a random challenge . Proto 2. c Alice Bob: MAC ( ). 3 ecure . ol Challenge-and-response using a secrete key k r y k r →= Bob computes MAC ( ) and checks if . 1. Alice Bob: a random challenge . 2. Alice Bob: ( ). 3. Bob checks if ( . Or ) k k k yr y y r yE r Dy r = = =
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MAC () Parallel sessions attack Alice Bob Eve k r yr r = ←⎯ ⎯⎯⎯⎯⎯→ ←⎯⎯⎯⎯⎯ ⎯⎯⎯ MAC ( ) k =
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MAC ( ) Bob M Count ermeasu r e Ev Ao e lice B b k r r r y y = = ←⎯⎯ ⎯⎯⎯⎯⎯⎯→ ←⎯ ⎯⎯⎯⎯⎯ ⎯⎯⎯ & AC ( Alice) k r &
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() : 1. Alice Alice and Bob share a secret key . se Protocol ID(Alic Bob: a random challenge . 2. Alice Bob: MAC ( ). 3. Bob c e) omputes M cure AC I ( Challenge-and-response using a secret key k k r k r y y →= = & ) and checks if . 1. Alice Bob: a random challenge . 2. Alice Bob: (ID(Alice) ). 3. Bob checks if ( ) ID D(Alice) Or (Alice) . k k r yy r yE r Dy r = = & & &
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1 2 11 Alice and Bob share a secret key .
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This note was uploaded on 01/22/2011 for the course CSE 651 taught by Professor Tenh.lai during the Spring '10 term at Ohio State.

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7.authen-key - Entity Authentication and Key Agreement CSE...

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