1. Encryption
Link Encryption
Common key cryptosystem
Public key cryptosystem
SSH
Group C
Takaaki Hukasawa
Saori Endo
Eitaro Miyamoto
Kazuhiro Matsumoto

2. Link Encryption
Make a direct link between sender and
reciever
In past, it used a private line.
Now, programs and routers allows us
to make a virtual direclink over the
internet

3. Common key cryptosystem
Use same key for encryption and decryption
Problem
We need to find a way to send a key safely
If the key was stolen, we need to make a new
key as soon as possible

4. Public key cryptosystem
Use two different keys. Those keys are
provided by reciever.
Key 1
It is open for people all over the world
It is used to encrypt a message
Only key two can decrypt the
encrypted message
It is called public key
Key 2
Only a receiver can use this key
It can decrypt a encrypted message with
key 1

5. Public key certificate
It uses a public key cryptosystem to certify
the user.
1. A sender uses a public key to encrypt a message to a receiver
2.The receiver use his/her private key to decrypt the message
3.The reviver send the message back to the sender
4.The sender can see that the receiver can decrypt the message
so the receiver is the person who the sender want to access.

6. References
Wikipedia
http://en.wikipedia.org/wiki/
msdn
http://msdn.microsoft.com/en-us/library/aa480610.aspx