MU CSCI 415 - Introduction to Cyrptography (19 pages)

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Introduction to Cyrptography



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Introduction to Cyrptography

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Pages:
19
School:
Millersville University
Course:
Csci 415 - Computer and Network Security
Unformatted text preview:

Introduction to Cryptography Flow 3 parts to Cryptography lecture in CSCI 415 Intro to Cryptography Symmetric Key Encryption Asymmetric Key Encryption digital signatures digital certificates digital envelopes SSL TLS 3 related lab components Dr Nazli Hardy Introduction to Cryptography Overview The fundamentals and history Character Level Encryption Substitutional Monoalphabetic Polyalphabetic Gronsfeld s System Vigenere Transpositional Bit Level Encryption Permutation Exclusive OR XOR Rotation Data Encryption Standard DES Advanced Encryption Standard AES International Data Encryption Algorithm Blowfish and RC5 block ciphers Dr Nazli Hardy Introduction to Cryptography Fundamentals Cryptography process of converting plaintext readable text into ciphertext unreadable encrypted text by authorized sender encryption Equally important is this system is the re conversion from unreadable to readable text by authorized recipient decryption Keys Symmetric Encryption Asymmetric encryption While cryptography obscures hides the meaning of the data from unauthorized user it does not hide the data itself what is that process called Dr Nazli Hardy Introduction to Cryptography History cryptography is nothing new Egyptian hieroglyphics found on ancient monuments were encrypted ca 4500 BC The Book of Jeremiah was written using a cipher or key known as atbash Connected with religious and academic literature and powers of the day Queen Elizabeth I ca 1550 Kama Sutra ca 2000 years ago recommends that men and women learn the art of cryptography Julius Caesar shifter letters by 3 positions i e a becomes d Used both in WW I and WW II Good book The Codebreakers David Kahn McMillan 1967 Dr Nazli Hardy Introduction to Cryptography War Machines Enigma machines used by Germans during WW II Developed by Arthur Scherbius How does it work The code was first broken by Polish cryptographers then by the British and Americans Dr Nazli Hardy Introduction to Cryptography Enigma Displayed at the National Cryptologic Museum 1 Commercial Enigma 2 Enigma T 3 Enigma G 4 Unidentified 5 Luftwaffe Air Force Enigma 6 Heer Army Enigma 7 Kriegsmarine Naval Enigma M4 Dr Nazli Hardy Introduction to Cryptography Symmetric and Asymmetric Cryptography Algorithms Type of Algorithm Description Symmetric Uses a single key to encrypt and decrypt data Both sender and receiver must agree on the key before the data is transmitted Support confidentiality but not authentication and nonrepudiation Faster than asymmetric algorithms Some difficulties Asymmetric Hashing Algorithm used for verification Takes a variable length input and converts it to a fixed length output strong called a hash value Uses 2 keys one to encrypt and one to decrypt data Support authentication and nonrepudiation Slower than symmetric algorithms Known as public key cryptography Article http www wired com news technology 0 1282 32263 00 html Dr Nazli Hardy Introduction to Cryptography Character Level Encryption Substitutional Monoalphabetic Caesar s Cipher Dr Nazli Hardy Introduction to Cryptography Character Level Encryption Substitutional Polyalphabetic Gronsfeld s System Key 7 3 4 1 7 3 4 1 7 Text G R O N S F E L D Crypto 7 A E I M Q U Y 3 B F J N R V Z 4 C G K O S W 1 D H L P T X more secure Writing the letters out row by row and starting with the row having the lowest keyfigure gives the following unordered sequence DHLPTXBFJNRVZCGKOSWAEIMQUY Key 7 3 4 1 7 3 4 1 7 Text G R O N S F E L D Crypto Dr Nazli Hardy Introduction to Cryptography Character Level Encryption Substitutional Standard Vigenere Vigenere Table Plaintext A T T A C K A T M I D N I G H T Plaintext Key Letter S E C U R I T Y S E C U R I T Y Key Letter A T T A C K A T M I D N I G H T Plaintext Key Letter Crypto S E C U R I X T Y S E C U R I T Y ABCDEFGHIJKLMNOPQRSTUVWXYZ BCDEFGHIJKLMNOPQRSTUVWXYZA CDEFGHIJKLMNOPQRSTUVWXYZAB DEFGHIJKLMNOPQRSTUVWXYZABC EFGHIJKLMNOPQRSTUVWXYZABCD FGHIJKLMNOPQRSTUVWXYZABCDE GHIJKLMNOPQRSTUVWXYZABCDEF HIJKLMNOPQRSTUVWXYZABCDEFG IJKLMNOPQRSTUVWXYZABCDEFGH JKLMNOPQRSTUVWXYZABCDEFGHI KLMNOPQRSTUVWXYZABCDEFGHIJ LMNOPQRSTUVWXYZABCDEFGHIJK MNOPQRSTUVWXYZABCDEFGHIJKL NOPQRSTUVWXYZABCDEFGHIJKLM OPQRSTUVWXYZABCDEFGHIJKLMN PQRSTUVWXYZABCDEFGHIJKLMNO QRSTUVWXYZABCDEFGHIJKLMNOP RSTUVWXYZABCDEFGHIJKLMNOPQ STUVWXYZABCDEFGHIJKLMNOPQR TUVWXYZABCDEFGHIJKLMNOPQRS UVWXYZABCDEFGHIJKLMNOPQRST VWXYZABCDEFGHIJKLMNOPQRSTU WXYZABCDEFGHIJKLMNOPQRSTUV XYZABCDEFGHIJKLMNOPQRSTUVW YZABCDEFGHIJKLMNOPQRSTUVWX ZABCDEFGHIJKLMNOPQRSTUVWXY Dr Nazli Hardy Introduction to Cryptography Character Level Encryption Substitutional Vigenere Standard Vigenere was the main cryptographic system used by the Confederated States during the American Civil War and four of the keyphrases used by the Confederates were IN GOD WE TRUST COMPLETE VICTORY MANCHESTER BLUFF COME RETRIBUTION The History of Codes and Ciphers in the United States prior to World War I Dr Nazli Hardy Introduction to Cryptography Character Level Encryption Substitutional Unordered Vigenere Plaintext A table using a body consisting of a mixed sequence based on the keyword SPHINX could look like this A T T A C K A T M I D N I G H T Plaintext Key Letter S E C U R I T Y S E C U R I T Y Key Letter A T T A C K A T M I D N I G H T Plaintext Key Letter Crypto S E C U R I N T Y S E C U R I T Y SPHINXABCDEFGJKLMOQRTUVWYZ PHINXABCDEFGJKLMOQRTUVWYZS HINXABCDEFGJKLMOQRTUVWYZSP INXABCDEFGJKLMOQRTUVWYZSPH NXABCDEFGJKLMOQRTUVWYZSPHI XABCDEFGJKLMOQRTUVWYZSPHIN ABCDEFGJKLMOQRTUVWYZSPHINX BCDEFGJKLMOQRTUVWYZSPHINXA CDEFGJKLMOQRTUVWYZSPHINXAB DEFGJKLMOQRTUVWYZSPHINXABC EFGJKLMOQRTUVWYZSPHINXABCD FGJKLMOQRTUVWYZSPHINXABCDE GJKLMOQRTUVWYZSPHINXABCDEF JKLMOQRTUVWYZSPHINXABCDEFG KLMOQRTUVWYZSPHINXABCDEFGJ LMOQRTUVWYZSPHINXABCDEFGJK MOQRTUVWYZSPHINXABCDEFGJKL OQRTUVWYZSPHINXABCDEFGJKLM QRTUVWYZSPHINXABCDEFGJKLMO RTUVWYZSPHINXABCDEFGJKLMOQ TUVWYZSPHINXABCDEFGJKLMOQR UVWYZSPHINXABCDEFGJKLMOQRT VWYZSPHINXABCDEFGJKLMOQRTU WYZSPHINXABCDEFGJKLMOQRTUV YZSPHINXABCDEFGJKLMOQRTUVW ZSPHINXABCDEFGJKLMOQRTUVWY Dr Nazli Hardy Introduction to Cryptography Character Level Encryption Transpositional The Key defines which columns are swapped 1 2 3 4 5 6 7 8 9 10 11 6 9 3 10 5 1 2 4 8 7 11 Encryption 1 2 a Decryption 3 4 5 6 g o o 7 8 9 10 11 1 d g o o d d f r i e n d i s b e t t e r t h a t r e a u r e a plaintext s 2 3 4 5 6 7 8 9 10 11 d n r a TRANSPOSE Encryption Algorithm TRANSPOSE Decryption Algorithm Ciphertext 1 2 3 4 5 6 7 8 9 10 11 Dr Nazli Hardy Introduction to Cryptography Bit Level


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