2. What is a VPN Public networks are used to move information between trusted network segments using shared facilities like frame relay or atm A VIRTUAL Private Network replaces all of the above utilizing the public Internet Performance and availability depend on your ISP and the Internet
32. Diffie-Hellman Public Key Exchange Private Value, X A Public Value, Y A Private Value, X B Public Value, Y B (shared secret) Alice Bob Y B mod p = g mod p = Y A mod p X B X A X B Y A Y B X A Y B = g mod p X B Y A = g mod p X A
11 43 43 Encryption is the masking of secret or sensitive information such that only an authorized party may view (or decrypt) it
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13 49 49 What is encrypted with the public key can only be decrypted with the private key. Anyone can encrypt with someone’s private key but only the intended recipient can decrypt What is encrypted with the private key can only be decrypted with the public key. Only the holder of the private key can encrypt, anyone can decrypt—proof of signature.
16 45 45 Diffie-Hellman Key Generation By exchanging numbers in the clear, two entities can determine a new unique number known only to them Result is a shared secret Neither party can alone control value Neither party knows—no needs to know—private key of other
17 Diffie-Hellmann exchange is based upon the concept of modular exponentiation. The prime p denotes a galois field. The numbers are HUGE—e.g,. 1024 bits
18 46 46 D-H exchange is in fact two exponentiations One exponentiation produces a “public value”. Private value is a random (but very large) number Public numbers are exchanged and another exponentiation is performed. Each party derives the same shared secret Susceptible to man-in-the-middle attack