APPLIED DATA COMMUNICATION
Tallinn University of Technology
Gülçin Yıldırım - Team #12
Encryption is the process of encoding messages or information in such a way that only authorized parties can read it.
Access and Availability
Actively insert messages into connection
Can fake (spoof) source address in packet (or any field in packet)
"Take over" ongoing connection by removing sender or receiver by inserting himself in place
Prevent service from being used by others (e.g, by overloading resources)
A Secret Message
A Secret Message
Requires two keys:
All communicating parties exchange their public keys
Sender encrypts the plaintext using receiver's public key
Receiver decrypts the ciphertext using their own private key
(share with pink)
(keep it secret)
(share with blue)
Private Key (keep it secret)
Trying to find a prize behind a series of number of doors
Public key encryption used to exchange keys
Symmetric key encryption used to encrypt data
Block Cipher and Stream Cipher
Operates on fixed-size blocks (N bits) and uses fixed-size keys (K bits)
One of the most popular block ciphers is the AES algorithm.
Some other examples are: DES, Blowfish, RC5, ...
There are four stages in the algorithm:
KeyExpansions: Keys are derived from the provided key
Rounds: SubBytes, ShiftRows, MixColumns, AddRoundKey
FinalRound: SubBytes, ShiftRows, AddRoundKey
Operates on variable-size blocks (N bits) and uses random-size keys
A popular stream cipher algorithm is RC4.
However, it is replaced by RC5, a block cipher algorithm.
The main concern of a key distribution method is how to securely supply keys between all communicating parties
There are some important security questions we must consider:
A key distribution method helps us with those concerns.
There are various different key distribution methods for different encryption types: