CST556: Cryptography
L1: Introduction
CST556
Course web site
http://users.wmin.ac.uk/~lancasd/CST556
40% Exam -- cryptographic theory in lectures
60% Coursework -- programming
Two assignments
1) handout during lab today, due 11th Feb
2) due 21st April
Books
Cryptography Decrypted H.Mel D.Baker
background reading for concepts
Cryptography and Network Security W.Stallings
serious content and detailed discussion
Cryptography for Internet and Database
Applications N.Galbreath for practical support
http://www.dawsonera.com/depp/reader/protected/external/AbstractView/S9780471428084
More books and details on web site
Contents
Math and programming
Symmetric Cryptography
Asymmetric Cryptography
Digital Signatures
Security Applications
Network protocols SSL, Email etc.
Lab Sessions
Some treatment of low level algorithms
bit manipulations C/Java
Quickly move to use of a cryptographic API
.NET/Java
manipulate keys/certificates
Support second assignment
What is Cryptography
used for?
Confidentiality: keep the message secret
Authentication: be certain where the
message came from
Integrity: ensure the message wasn’t altered
Non-repudiation: so someone cannot deny
sending the message
Secrecy, Authentication
Secrecy: Traditional military use of
Cryptography to hide information and ensure
that no one else has access to it
Authentication: If you can successfully
decrypt a message with a certain key, and
find a correct checksum, you can presume
that the message was encrypted by the
holder of the corresponding encryption key
Today: Keys
First 2 weeks just secrecy - will return to
other uses in lecture 3
Classical cryptography - modern
cryptography next week
Cryptography Decrypted ch 1 and 2 - read
these by next week
Obfustication: restricted
algorithms
To hide something from your kid sister
Some arbitrary obscure trick you invent
Algorithm is restricted
That is not what modern cryptography is about
Algorithm is public – well tested
Security lies in key selection
Problems with restricted
algorithms
They w