1. Privacy & Security

2. Privacy & Security
Individuals lump together as “it’s hard to feel safe and secure if aspects of your personal life are widely known or easy to find out.”

3. Cryptography The art of secret writing
The best defense against attacks

4. Caesar Cipher Move so many over – like 3 – in the alphabet
HI JULIUS  KL MXOLXV
rot13 program
Used today on newsgroups to hide spoilers and offensive material
Not for cryptography purposes

5. Cryptography
Basic idea: Allice & Bob want to exchange messages, keeping the contents private, but not fact threat they are communicating

6. Secret-Key Cryptography
A message is encrypted and decrypted with the same secret key
The key must be shared by all parties who want to exchange messages
Only way to decrypt without the key is brute force
Meaning – to try all the possibilities
This does not mean dumb!
Will try the common ones fist, or short ones first; in essence the likely one before trying the unlikely one
i. e. password for a person’s password

7. DES: Dara Encryption Standard
Used 1976 to the early 2000’s
Developed by IBM & NSA
56-bit key

8. AES: Advanced Encryption Standard
Official US government standard in 2002
Supports 3 lengths: 128, 192, and 256 bits
Can’t win with brute force
Is have a million GPs that can do 1019 operations per second that would be about 290; meaning not enough in one year to guess 2128 possibilities
Problem: key distribution
Problem: key proliferation

9. Public Key Cryptography
1976 by Whitfield Diffie and Martin Hellman at Stanford
Also by James Ellis and Clifford Cocks at the British intelligence agency GCHQ and kept secret until 1997
Each person has a key pair ( a private key & a public key)
Public key: available to everyone, even posted on a web page
Private Key: strictly private – only to the owner
a message is encrypted with a recipient's public key. The message cannot be decrypted by anyone who does not possess the matching private key, who is thus presumed to be the owner of that key and the person associated with the public key. This is used in an attempt to ensure confidentiality.
Fixes the distribution of the keys
Examples in use: https, digital signature

10. Public – Private Key Cryptography
An unpredictable (typically large and random) number is used to begin generation of an acceptable pair of keys suitable for use by an asymmetric key algorithm.
In an asymmetric key encryption scheme, anyone can encrypt messages using the public key, but only the holder of the paired private key can decrypt. Security depends on the secrecy of the private key.
In the Diffie–Hellman key exchange scheme, each party generates a public/private key pair and distributes the public key. After obtaining an authentic copy of each other's public keys, Alice and Bob can compute a shared secret offline. The shared secret can be used, for instance, as the key for a symmetric cipher.

11. Forward Secrecy
Each individual message is encrypted with a one-time password and then the password is disgarded

12. RSA Ronald Rivest & Adi Shamir & Leonard Adleman at MIT in 1978
A large integer generated from 2 large prime numbers
The 2 prime integers are the public & private keys