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Unformatted text preview: an secret key ones. One should
algorithms
One
avoid using public key algorithms to encrypt large amount of data
(long messages)
(long Use Publickey encryption to “seal” a digital
envelope The sender picks a “secret” Session Key to encrypt the long message
The
using a secret key algorithm, e.g. AES.
using
By encrypting the session key with the Recipient’s public key, the
By
session key can be delivered securely to the recipient without any presession
shared secret between the 2 parties
Conversely, we can consider this as doing a secure sessionkey
Conversely,
exchange using public key encryption
exchange History of Public Key Cryptography in “public”
world Diffie was a graduate student in Stanford, working with Prof. Hellman on
Diffie
solving the “key distribution problem”.
solving
They proposed the concept of a “PublicKey Cryptosystem” (PKC). (This
They
concept
remarkable idea developed jointly with Merkle.) which can:
remarkable solve the key distribution problem of a symmetric key system and Even more amazingly, introduce the notion of digital signature
However, they were unable to find the necessary functions to realize such a
However,
were
system, namely, to find a pair of functions D( ) and E( ) such that:
system,
D(E(m)) = E(D(m)) = m and
D( ) can be kept secret while E( ) is known to the public
E(
It is impossible to derive D( ) by knowing E( )
It
D(
E(
Instead, they were able to find a way for communication parties to establish
Instead,
a shared secret via open communications only
shared
=> This is the DiffieHellman Key exchange algorithm
=> The Beginning of Public Key Cryptography in
“public” world (cont’d) Diffie and Hellman published their ideas and findings in “New
Diffie
Directions in Cryptography” Nov ’76, together with the open problem
of realizing PKC
of
Ron Rivest saw Diffie and Hellman’s paper and was intrigued by it.
Ron
He enlisted the help of Shamir and Adleman, all from MIT, to work on
the open problem and came up with the solution in 1977  this is the
RSA algorithm
RSA
Diffie, Hellman, Merkle, Rivest, Shamir, Adleman were commonly
Diffie,...
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 Fall '13
 CHOWSzeMing,Sherman

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