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Cryptography.ppt
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- 3. Overview Basic Definitions History of Cryptography Cipher Types Cryptography Methods Common Types of Attacks
- 4. Definitions - Cryptology Cryptography Cryptanalysis Steganography Cryptosystem
- 5. Cryptography is everywhere Secure communication: –web traffic: HTTPS –wireless traffic: 802.11i WPA2 (and WEP), GSM, Bluetooth Encrypting files on disk: EFS, TrueCrypt Content protection (e.g. DVD, Blu-ray): CSS, AACS User authentication … and much much more
- 6. History of Cryptography The first known evidence of the use of cryptography (in some form) was found in an inscription carved around 1900 BC, in the main chamber of the tomb of the nobleman Khnumhotep II, in Egypt. Around 400 B.C., the Spartans used a system of encrypting information by writing a message on a sheet of papyrus. Around 100 B.C., Julius Caesar was known to use a form of encryption to convey secret messages to his army generals posted in the war front.
- 7. During the16th century, Vigenere designed a cipher that was supposedly the first cipher which used an encryption key. At the start of the 19th century when everything became electric, Hebern designed an electro-mechanical contraption which was called the Hebern rotor machine.
- 8. The Engimamachine was invented by German engineer Arthur Scherbius at the end of World War I, and was heavily used by the German forces during the Second World War.
- 9. IBM inearly 1970s designed a cipher called Lucifer. Lucifer was eventually accepted by NIST and was called DES or the Data Encryption Standard. In 2000, NIST accepted Rijndael, and named it as AES or the Advanced Encryption Standard.
- 10. Ciphers In cryptography, acipher is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment.
- 11.
- 12. Stream cipher AStream Cipher is a secret-key encryption algorithm that encrypts a single bit at a time. With a Stream Cipher, the same plaintext bit or byte will encrypt to a different bit or byte every time it is encrypted. e.g. : Plain text: Pay 100 Binary of plain text: 010111101 (hypothetical) Key: 100101011 ----- Perform XOR ____________________ Cipher text 110010110 ----- ZTU9^%D To decrypt make the XOR operation of the cipher text with the key .
- 13. Block cipher Blockcipher technique involves encryption of one block of text at a time .Decryption also takes one block of encrypted text at a time. Length of the block is usually 64 or 128 bits. e.g. : Plain text: four and five Four and five Key Key Key wvfa ast wvfa --- cipher text
- 14. Public Key Cryptosystem Public key cryptography is a scheme that uses a Pair of keys for encryption: a Public key, which encrypts data, and a corresponding Private key (secret key) for decryption.
- 15. CRYPTOGRAPHY METHODS Symmetric Same key for encryption and decryption Key distribution problem Asymmetric Key pairs for encryption and decryption Public and private keys
- 16. Symmetric Algorithm Itis also called as Secret Key Cryptography Single key used for both encrypt & decrypt Key must be known to both the parties Encryption Decryption Key Plaintext Ciphertext Original Plaintext Symmetric Cryptosystem
- 17. Symmetric Algorithm DataEncryption Standard (DES): 56 bits key Advance Encryption Standard (AES): 128, 192 or 256 bits key International Data Encryption Algorithm(IDEA): 128 bits key
- 18. Asymmetric Algorithm Privatekeys are used for decrypting. Public keys are used for encrypting encryption plaintext ciphertext public key decryption ciphertext plaintext private key
- 19. Hybrid cryptosystem Ahybrid cryptosystem can be constructed using any two separate cryptosystems: a key encapsulation scheme, which is a public-key cryptosystem, a data encapsulation scheme, which is a symmetric-key cryptosystem.
- 20. COMMON TYPES OFATTACKS Brute force Trying all key values in the keyspace. Chosen Ciphertext Decrypt known ciphertext to discover key. Dictionary Attack Find plaintext based on common words. Frequency Analysis Guess values based on frequency of occurrence.
- 21. References An introductionto cryptography and cryptanalysis -Edward Schaefer,Santa Clara University http://en.wikipedia.org/wiki/History_of_cryptography https://securityblog.redhat.com/2013/08/14/a-brief-history-of- cryptography/ Contemporary Cryptography - Rolf Oppliger Cryptography Theory And Practice - Douglas Stinson Modern Cryptography Theory and Practice - Wenbo Mao
- 22. One must acknowledgewith cryptography no amount of violence will ever solve a math problem ― Jacob Appelbaum, Cypherpunks: Freedom and the Future of the Internet
Editor's Notes
- #12 The Pigpen cipher (sometimes called the Masonic cipher or Freemason's cipher) is a simple substitution cipher exchanging letters for symbols based on a grid (or the "pigpen") surrounding it.