Cairo University
Institute of Statistical Studies and Research
Computer Science Dept.
Cs515 - Is517
Computer Security
Sheet1
1. InRSAForp=5,q=7.Ande=5getthepublickey
2. Encryptthefollowingmessageusing
LECTURE 8
KEY MANAGEMENT
Key Management: process of generating, storing,
agreeing upon and revoking keys
KEY MANAGEMENT WHAT IS IT?
Assuming that youve selected an appropriate,
well vetted symmetric e
Lecture 4
Data Encryption Standard (DES)
Dr. Nermin Hamza
1
From Classical Ciphers to Modern Ciphers
Classical Cipher Modern Cipher (Block
cipher)
Alphabetic letters Binary data
Easy to do
Large bl
Lecture 7
Authentication and Digital Signature
Dr. Nermin Hamza
Authentication Requirements
Attacks:
Traffic Analysis : traffic analysis occurs when
an eavesdroppers observes message traffic on
netwo
Lecture 2 2013
Classical Encryption Techniques
Dr. Nermin Hamza
1
Introduction
Cryptography
Cryptography is the science of writing insecret code and is an ancient art .
The first documented use of
Lecture 3
1
TRANSPOSITION CIPHERS
2
Transposition Ciphers
now consider classical transposition or
permutation ciphers
these hide the message by rearranging the
letter order
without altering the actu
Lecture 5
Asymmetric Cryptography
Private-Key Cryptography
Traditional private/secret/single key
cryptography uses one key
Shared by both sender and receiver
If this key is disclosed communications
WHAT ABOUT THE KEY
1
Sub-key Generation
2
Permutation Choice
Note:
Only 56 bits
Are used
3
Each Iteration Uses a Different Sub-key
DES works on 64 bits of data at a time. Each
64 bits of data is iter
Lecture 6
RSA Use in Encryption
to encrypt a message M the sender:
obtains public key of recipient PU=cfw_e,n
computes: C = Me mod n, where 0M<n
to decrypt the ciphertext C the owner:
uses their