密码学及网络安全 第二讲.pptx

密码学与网络安全
第二讲传统加密技术
Outline
Course reviews
Cryptography & Steganography
Basic concepts of cryptography
Cryptanalysis and brute-force attack
Roadmap of cryptography
Classical Cipher
Substitution & Permutation Cipher
2018/2/20
2
OSI Security Architecture
2018/2/20
3
2018/2/20
4
Cryptography & Steganography
Cryptography
Greek origins, means secret writing
It encodes a message so it cannot be understood
Steganography
Greek origins, means covered writing
Art of hiding information in ways that prevent the detection of hidden message, Existence is not known
2018/2/20
5
Steganography
Example: covering data with text
We can use single space between words to represent the binary digit 0 and double space to represent binary digit 1. The following short message hides the 8-bit binary representation of the letter A in ASCII code 01000001.
2018/2/20
6
Steganography
Fishing freshwater bends and saltwater coasts rewards anyone feeling stressed. Resourceful anglers usually find masterful leapers fun and admit swordfish rank overwhelming anyday
Send Lawyers, Guns, and Money
Simmons Prisoner's Problem, The prisoners' problem and the subliminal channel
2018/2/20
7
Cryptography is everywhere
munication
SSL/TLS, WEP, WPA2,
Encrypting files on disk
EFS, TrueCrypt
Content protection (. DVD, Blu-ray)
CSS, AACS
User authentication, ……
2018/2/20
8
Building Block
Encryption algorithm is publicly known
Never use a proprietary cipher
2018/2/20
9
Crypto core
2018/2/20
10
Secret key
Establishment
Secure
Communication
attacker???
k
k
confidentiality and integrity
m1
m2
Alice
Bob
Talking to Alice
Talking to Bob