CM30173: Cryptography\reserved@d =[@let@token art II
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
Part II
Private-key cryptography: block ciphers
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
The Data Encryption Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook mode (ECB)
Cipher block chaining mode (CBC)
Output feedback mode (OFB)
Cipher feedback mode (CFB)
Further reading
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
Diagram of ECB
k
xi
yi
ek
Try this:
Find a small bitmap file picturing
a sharply defined object
Encrypt the bitmap using your
SPN
View the resulting bitmap
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
Diagram of CBC
IV = y0 . . .
kk
x1
y1
x2
y2
ekek
Try this (cont):
Implement CBC mode for your SPN
Encrypt the same bitmap using CBC
View the resulting bitmap
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
Diagram of OFB
PSfrag replacements IV = z0 . . .
kk
x1
y1
z1
x2
y2
z2
ekek
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
Diagram of CFB
IV = y0 . . .
kk
x1
y1
z1
x2
y2
z2
ekek
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
The Data Encryption Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook mode (ECB)
Cipher block chaining mode (CBC)
Output feedback mode (OFB)
Cipher feedback mode (CFB)
Further reading
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
Directed reading
D. Coppersmith. The Data Encryption Standard (DES)
and its strength against attacks, IBM J. R & D,
38:243-250, 1994
What were the design criteria that were used in
DES to protect it against di!erential cryptanalysis?
What was the general aim of these criteria?
Try to write a short summary describing the paper.
CM30173:
Cryptography
Part II
The Data
Encryption
Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook
mode (ECB)
Cipher block chaining
mode (CBC)
Output feedback mode
(OFB)
Cipher feedback mode
(CFB)
Further reading
Additional sources of information
1 Data Encryption Standard (DES). FIPS Publication
46, 1977.
2 DES Modes of Operation. FIPS Publication 81,
1980
3 Guidelines for Implementing and Using the NBS
Data Encryption Standard. FIPS Publication 74,
1981
4 Computer Data Authentication. FIPS Publication
113, 1985
Private-key cryptography: block ciphers
The Data Encryption Standard (DES)
Feistel ciphers
DES
Security of DES
Modes of operation
Electronic codebook mode (ECB)
Cipher block chaining mode (CBC)
Output feedback mode (OFB)
Cipher feedback mode (CFB)
Further reading