01-08-2012, 01:10 PM
NETWORK SECURITY
Network Security.ppt (Size: 2.08 MB / Downloads: 49)
An Introduction to Cryptography
Impractical to keep encryption and decryption algorithms private
Large overhead to redesign and re-implement
Solution:
Secret key that can be changed as needed
Secrecy lies exclusively with the key
Longer key = greater security
Symmetric-Key Algorithms
DES – The Data Encryption Standard
AES – The Advanced Encryption Standard
Cipher Modes
Other Ciphers
Cryptanalysis
Keys
Different subkey for each iteration
Before algorithm: 56-bit transposition on key
Before iteration:
key partitioned into two 28 bit values
Each rotated some number of bits
Ki derived from these by performing another 56 bit transposition
The 48 bit subkey derived from Ki
AES – The Advanced Encryption Standard
The algorithm must be a symmetric block cipher.
The full design must be public.
Key lengths of 128, 192, and 256 bits supported.
Both software and hardware implementations required
The algorithm must be public or licensed on nondiscriminatory terms.
Network Security.ppt (Size: 2.08 MB / Downloads: 49)
An Introduction to Cryptography
Impractical to keep encryption and decryption algorithms private
Large overhead to redesign and re-implement
Solution:
Secret key that can be changed as needed
Secrecy lies exclusively with the key
Longer key = greater security
Symmetric-Key Algorithms
DES – The Data Encryption Standard
AES – The Advanced Encryption Standard
Cipher Modes
Other Ciphers
Cryptanalysis
Keys
Different subkey for each iteration
Before algorithm: 56-bit transposition on key
Before iteration:
key partitioned into two 28 bit values
Each rotated some number of bits
Ki derived from these by performing another 56 bit transposition
The 48 bit subkey derived from Ki
AES – The Advanced Encryption Standard
The algorithm must be a symmetric block cipher.
The full design must be public.
Key lengths of 128, 192, and 256 bits supported.
Both software and hardware implementations required
The algorithm must be public or licensed on nondiscriminatory terms.