Stream Cipher
,Topics
One-Time-Pad
Random Number Generator
Stream Cipher
RC4
RC4 and WEP
, One-Time Pad
Developed by Gilbert Vernam in 1918, another name: Vernam Cipher
The key
a truly random sequence of 0’s and 1’s
the same length as the message
use one time only
• The encryption
• adding the key to the message modulo 2, bit by bit.
Encryption
Decryption
mi : plain-text bits.
ki : key (key-stream ) bits
ci : cipher-text bits.
,Topics
One-Time-Pad
Random Number Generator
Stream Cipher
RC4
RC4 and WEP
, One-Time Pad
Developed by Gilbert Vernam in 1918, another name: Vernam Cipher
The key
a truly random sequence of 0’s and 1’s
the same length as the message
use one time only
• The encryption
• adding the key to the message modulo 2, bit by bit.
Encryption
Decryption
mi : plain-text bits.
ki : key (key-stream ) bits
ci : cipher-text bits.
