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# Information Cryptography Security

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### Information Cryptography Security

1. 1. Information Cryptography & Security Week 7
2. 2. Information Security & Authentication <ul><li>Cryptography </li></ul><ul><li>Derived from the Greek word kryptos (meaning ‘hidden’) </li></ul><ul><li>The aim of Cryptography is to hide its meaning , rather than the existence of a message </li></ul><ul><li>Cryptography can be divided into 2 branches, such as: </li></ul><ul><li>1. Transposition </li></ul><ul><li>2. Substitution </li></ul>
3. 3. Cryptographic Methods <ul><li>1. The Rail-Fence Transposition </li></ul><ul><li>It is a transposition cryptography in which the message is written with alternate letters on separate upper and lower lines. </li></ul><ul><li>For instance: “Rail-Fence” Transposition Cryptography </li></ul>(Singh, 2000)
4. 4. Cryptographic Methods <ul><li>2. The Spartan scytale </li></ul><ul><li>Other transposition cryptography in the military device </li></ul><ul><li>The Scytale is a wooden staff around which a strip of leather or parchment is wound. </li></ul><ul><li>For instance: Spartan scytale </li></ul>(Singh, 2000)
5. 5. Cryptographic Methods <ul><li>3. The Caesar Shift Cipher </li></ul><ul><li>By substitution, Julius Caesar replaced each letter in the message with the letter that is 3 places further down the alphabet. </li></ul><ul><li>For instance: “The Caesar Cipher” </li></ul>(Singh, 2000)
6. 6. Cryptographic Methods <ul><li>4. The Vigenere Square cipher </li></ul><ul><li>The Vigenere cipher lies in using 26 distinct cipher alphabets. </li></ul><ul><li>For instance: </li></ul>(Singh, 2000)
7. 7. Cryptographic Methods <ul><li>Form of transposition cipher </li></ul>(Singh, 2000)
8. 8. Exercises <ul><li>Encrypt a message: “SBY IS OUR PRESIDENT” in the Rail-Fence transposition cipher, the Caesar cipher, and the Vigenere cipher. For Vigenere cipher, the key = “SUHENDRO”. </li></ul><ul><li>Encrypt a message: “ALO” by using Key = “TOP” in binary numbers with a simple transposition cipher. </li></ul>
9. 9. Older Cryptographic Machine <ul><li>Enigma Machine </li></ul><ul><li>In the World War II, a German cryptographic machine was invented by Arthur Scherbius. </li></ul>(Singh, 2000)
10. 10. Modern Cryptography <ul><li>Other Cryptographic methods: </li></ul><ul><li>1. Secret Key Cryptography </li></ul><ul><li>2. Public Key Cryptography </li></ul>
11. 11. Modern Cryptography <ul><li>1. “Secret Key” Cryptography </li></ul><ul><li>It uses a secret key such as Data Encryption Standard (DES) </li></ul><ul><li>DES is a National Institute of Standards & Technology (NIST) standard key cryptography method that uses a 56-bit key. </li></ul><ul><li>( http:// www.nist.gov ) </li></ul><ul><li>DES lets both sender and receiver use the same key </li></ul><ul><li>to encrypt or decrypt. </li></ul>
12. 12. Modern Cryptography <ul><li>1. Process of “Secret Key” Cryptography </li></ul>Ref: http://dret.net/lectures/web-fall08/img/secret-key.gif
13. 13. Modern Cryptography <ul><li>2. “Public Key” Cryptography </li></ul><ul><li>It uses a private key (kept by owner) & public key is published </li></ul><ul><li>The public key uses a standard RSA (Rivest-Shamir-Adleman) Data Security, Inc. Redwood City, CA. </li></ul><ul><li>( http:// www.rsa.com ) </li></ul><ul><li>It is more secured than a secret key cryptography </li></ul>
14. 14. Modern Cryptography <ul><li>2. Process of “Public Key” Cryptography </li></ul>Ref: http://dret.net/lectures/web-spring09/img/public-key-secret-encrypt.gif
15. 15. Digital Signature <ul><li>The ‘signature’ is an encrypted digest of the file (text message, </li></ul><ul><li> executable, etc) </li></ul><ul><li>Digital Signature uses hash functions to the message along </li></ul><ul><li>with a private key. </li></ul><ul><li>The message’s signature generates according to PGP </li></ul><ul><li>(Pretty Good Privacy) or SMIME (Secure Multipurpose Internet </li></ul><ul><li>Mail Extensions) standards. </li></ul><ul><li>Note: PGP is a software widely used for signing and </li></ul><ul><li> encrypting email messages. </li></ul>
16. 16. Digital Signature <ul><li>Process of Digital Signature Authentication </li></ul>Ref: http://www.infosec.gov.hk/english/itpro/images/digital_signature.gif
17. 17. Digital Certificate <ul><li>Digital Certificate (Certs) ensures if a public key belongs to the owner. </li></ul><ul><li>Digital Certificate (Certs) consists of: </li></ul><ul><li>1. A public key </li></ul><ul><li>2. Certificate Information </li></ul><ul><li>(i.e.: Identity of user, such as name, userID, etc) </li></ul><ul><li>3. One or more Digital Signature </li></ul>
18. 18. Digital Certificate <ul><li>Example: Digital Certificate </li></ul>Ref: http://www.mysecurecyberspace.com/encyclopedia/index/digitalcertificate.pic1.jpeg Ref: http://media.photobucket.com/image/digital%20certificate%20image/msanto/One-Offs2009/GearsofWarDigitalCertificate.jpg
19. 19. Digital Watermark <ul><li>A pattern of bits embedded into a file used to identify </li></ul><ul><li>the source of illegal copies. </li></ul><ul><li>If a digital watermark is placed into a master copy of </li></ul><ul><li>an audio CD, DVD, file, etc then all copies of that disc are </li></ul><ul><li>uniquely identified. </li></ul><ul><li>Example: </li></ul>Ref: http://www.bytescout.com/images/examples/watermarking/watermarked_image_sample_text_fits_page.png
20. 20. References <ul><li>Singh, S. (2000).The Code Book </li></ul><ul><li>Freedman, A. (2001). Computer Desktop Encyclopedia </li></ul>