1. Encryption: Image Representation Privacy/Cryptography

2. Information Security for…
Defending against external/internal hackers
Defending against industrial espionage
Securing E-commerce
Securing bank accounts/electronic transfers
Securing intellectual property
Avoiding liability
Pervasiveness of /networks
Online storage of sensitive information
Insecure technologies (e.g., wireless)
Trend towards paperless society
Weak legal protection of privacy

3. History 50 B.C. Julius Caesar uses cryptographic technique
1466 Leon Alberti develops a cipher disk
1861 Union forces use a cipher during Civil War
1919 Germans develop the Engima machine
for encryption
1942 Navajo windtalkers help with secure
communication during World War II
1948 Claude Shannon develops statistical
methods for encryption/decryption
1976 IBM develops DES
1976 Diffie – Hellman develop public key /
private key cryptography
1977 Rivest – Shamir – Adleman develop the
RSA algorithm for public key / private key

4. Basic Terminology
Cryptography deals with creating documents that can be shared secretly over public communication channels
Cryptographic documents are decrypted with the key associated with encryption, with the knowledge of the encryptor
The word cryptography comes from the Greek words: Krypto (secret) and graphein (write)
Cryptanalysis deals with finding the encryption key without the knowledge of the encryptor
Cryptosystems are computer systems used to encrypt data for secure transmission and storage

5. Types of Secret Writing
Steganography
Cryptography
Substitution
Transposition
Code
Cipher

6. Basic Terminologies
Steganography is the practice of concealing messages or information within other nonsecret text or data. The goal is to hide information. Encryptions goal is to make information unreadable .
Steganography does not increase file size for hidden messages

7. Steganography Videos
- Watch until 5:15

8. Steganography Examples
The simplest approach to hiding data within an image file is called least significant bit (LSB) insertion. In this method, we can take the binary representation of the hidden_data and overwrite the LSB of each byte within the cover_image. If we are using 24-bit color, the amount of change will be minimal and indiscernible to the human eye. As an example, suppose that we have three adjacent pixels (nine bytes) with the following RGB encoding:

9. Example:
Now suppose we want to "hide" the following 9 bits of data (the hidden data is usually compressed prior to being hidden): If we overlay these 9 bits over the LSB of the 9 bytes above, we get the following (where bits in bold have been changed):

10. Steganography
Steganography – covered writing – is an art of hiding information
Popular contemporary steganographic technologies hide information in images
New York Times, August 3rd, 2001

11. Hiding information in pictures

12. Hiding information in pictures

13. Questions
Please complete the question sheet over Steganography and Cryptography.

14. Caesar Cipher
A substitution cipher where each plaintext letter is replaced by some letter a fixed number of spaces down in the alphabet

15. Caesar Cipher
Open the following link
Watch the first two videos (What is cryptography and The Ceaser Cipher
Go to the third link and open up the Ceaser Cipher Exploration and complete the worksheet.

16. Basic Terminologies
Keys are rules used in algorithms to convert a document into a secret document
Keys are of two types:
Symmetric
Asymmetric
A key is symmetric if the same key is used both for encryption and decryption
A key is asymmetric if different keys are used for encryption and decryption

17. ROT13 Network data encryption / decryption using ROT13 algorithm
Rotates characters by 13 places
‘A’  ‘N’, ‘M’  ‘Z’, ‘a’  ‘n’, ‘m’  ‘z’
Encryption Example:
‘Hello World’ encrypts to ‘Uryyb Jbeyq’
Decryption Example:
‘Uryyb Jbeyq’ decrypts to ‘Hello World’

18. Public Key Cryptography
Private (symmetric, secret) key – the same key used for encryption/decryption
Problem of key distribution – how to get the key safely into hands of both parties
Public (asymmetric) key cryptography – a public key used for encryption and private key for decryption
Key distribution problem solved
Very popular technique:
Large Prime Numbers

19. Transmitting over an insecure channel
Alice wants to send Bob a private message.
Apublic is Alice’s public key.
Aprivate is Alice’s private key.
Bpublic is Bob’s public key.
Bprivate is Bob’s private key.

20. Hello Bob, Wanna get together?
Alice
Bob
encrypt using Bpublic
decrypt using Bprivate

21. OK Alice, where do we meet?
Bob
decrypt using Aprivate
encrypt using Apublic

22. Bob’s Dilemma: Authenticity of Communication
Nobody can read the message from Alice, but anyone could produce it.
How does Bob know that the message was really sent from Alice? What if it was from ex-girlfriend, Suzy?
Bob may be comforted to know that only Alice can read his reply.

23. Alice can sign her message!
Alice can create a digital signature and prove she sent the message (or someone with knowledge of her private key).
The signature can be a message digest encrypted with Aprivate.
Helps to prevent:
Impostor attacks
Content tampering

24. Digital Certificates
Issued by trusted third parties known as Certificate Authorities (CAs)
Verisign is a trusted third party
Used to authenticate an individual or an organization
Digital Certificates are usually given for a period of one year
They can be revoked
It is given at various security levels. The higher the security level, the CA verifies the authenticity of the certificate seeker more.

25. Digital Certificates
Digital Certificates are part of the authentication mechanism. The other part is Digital Signature.
When a user uses the digital signature, the user starts with their private key and encrypts the message and sends it. The receiver uses the sender’s public key and decrypts the message
In traditional encryption, the sender uses the public key of the receiver and encrypts the message and sends it and the receiver decrypts the message with their private key

26. Potential Problems with Cryptographic Technologies?
False sense of security if badly implemented
Government regulation of cryptographic technologies/export restrictions
Encryption prohibited in some countries

27. Video Example Example of public key cyrptography using color mixing

28. Privacy

29. Criminals Caught by Bits
Dennis Rader, the “BTK Killer”
Killed 10 people over 17 year period
Arrested in 2005
From Wikipedia:
“Police found metadata embedded in a deleted Microsoft Word document that was, unbeknownst to Rader, on the disk. The metadata, recovered using the forensic software EnCase, contained "Christ Lutheran Church", and the document was marked as last modified by "Dennis". A search of the church website turned up Dennis Rader as president of the congregation council. Police began surveillance of Rader.

30. Criminals Caught by Bits
Video:
36:40 – 38:00