The Idea of Public Key Cryptography

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21 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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The Idea of Public Key
Cryptography


Cunsheng Ding

HKUST, Hong Kong

The Idea of Public Key Cryptography

Locking key

Unlocking key


Put (lock, locking key) in
the public domain, i.e., in
a post office.


Anyone who wants to
send me a letter
confidentially can do the
following:


Buy a strong box


Use my lock with the
locking key to lock the
letter inside.


Send me the locked box.


Encryption with a Public Key System


file

file

encryted

file

Bob

Alice

Alice’s

public

Key k

Alice’s

Private

Key k



m


m

e

d

E (m)


k

e

(k , k ) is the key pair

of Alice

e

d

Digital Signature with a public key system


m

f

f(m)

D (f(m))

k

d

m||D (f(m))

d

k

m

f(m)

Bob

Alice

(k , k ) is Bob’s

key pair

e

d

Key Exchange with a Public Key System


session

key

session

key

encryted

sess. key

Bob

Alice

Alice’s

public

Key k

Alice’s

Private

Key k



k



k

e

d

E (k)


k

e

Bob generates the session key k, sends Alice the encrypted session key.

(k , k ) is the key pair

of Alice


e

d