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## Cryptography

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**Cryptography**Past, Present, and Future Presenter: Group 3 Ahmed Abdalla,Troy Brant, Gabe Campbell, Ana Lim, Saudamini Zarapkar**Outline**A Brief History of Cryptography Symmetric Encryption Asymmetric Cryptography Politics in Cryptography Quantum Cryptography Summary**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Brief History of Cryptography • Ancient times • Substitution ciphers - method of encrypting by which units of plaintext are substituted with cipher text according to a regular system. • EX: Atbash cipher (circa 500 BC) • based on Hebrew alphabet, • where the first letter is substituted by the last letter, the second letter by the second to last letter and so on.**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary History (continue) • Frequency analysis - where one examines the frequency of substituted letters, from which they can estimate certain letters which appear repeatedly in the plaintext language. • First recorded use in 9th century.**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary History (continue) • Polyalphabetic Cipher • Based on substitution, but used multiple substitution alphabets. • Invented by Leon Battista Alberti in 1467.Alberti would use a common Caesar cipher to encrypt messages, but would switch alphabet keys, indicating switch by capitalizing the first letter of the new alphabet.**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary History (continue) • Cryptanalysis of Polyalphabetic Cipher • Charles Babbage • 1854 – He found that the critical weakness in a polyalphabetic was the short and repetitive nature of the key. • Freidrich Kasiski • 1863 – published Die Geheimschriften und die Dechiffrierkunst that was first published account of deciphering polyalphabetic ciphers, especially the Vigenère cipher.**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary History (continue) • Babbage/Kasiski Test Ciphertext: DYDUXRMHTVDVNQDQNWDYDUXRMHARTJGWNQD • Look for repeated groups of letters and count the number of letters between the beginning of each group. • Factor the numbers. If there are similarities, that is the length of the key. • If the keyword is N letters long, then every Nth letter must be enciphered using the same letter of the keytext. Grouping every Nth letter together, it is possible to use frequency analysis to decipher message.**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary History (continue) • WWII Innovations • Electromechanical rotor machines that worked with any combination rotors • Enigma famous for its messages that were decrypted by Allied forces – intel known as ULTRA.**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary History (continue) • One-Time Pads • Developed in 1917 by Gilbert Vernam, an AT&T Bell Labs engineer. • OTP is an encryption algorithm where the plaintext is combined with a random key that is as long as the plaintext so that it’s used only once. • OTP proven unbreakable by Claude Shannon, a fellow engineer at Bell Labs who provided a proof in his information theory.**Outline**• A Brief History of Cryptography • Symmetic Encryption • Asymmetic Cryptography • Politics in Cryptography • Quantum Cryptography • Summary**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Symmetric Encryption • Overview • The Serpent Algorithm • The TwoFish Algorithm**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Symmetric (Continue) • Overview • DES • Invented by IBM • In 1976 became an official Federal Information Processing Standard (FIPS) NIST • Effective key length 56-bit • Double DES, Triple DES**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Symmetric (Continue) NIST contest • the First AES Conference • August 20, 1998 • 15 candidate algorithms • 5 US, 10 international • the Second AES Conference • March 22, 1999 • Technical Analysis • Announcement of 5 finalists • Mars, RC6, Rijndeal, Serpent, and TwoFish • the Third AES Conference • April 13, 2000 • Winner: Rijndeal**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Symmetric Encryption • The Serpent Algorithm • Second place • Designed by Ross Anderson, Eli Biham and Lars Knudsen • Substitution-Permutation Network • S-boxes: transform input bits into output bits • P-boxes: permute or transpose bits across S-box inputs.**Symmetric Encryption**• The Serpent Algorithm • a block size of 128 bits • key length vary from 128 to 256 bits long • 33 128-bit subkeys • 32 rounds**Symmetric Encryption**• The Serpent Algorithm • Algorithm: • initial permutation • 32 rounds of Key Mixing, pass through S-boxes, • and linear tranf ormation • a final permutation**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary The Serpent Algorithm**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary The Serpent Algorithm**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary The Serpent Algorithm**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Symmetric Encryption • The Serpent Algorithm • Hardware • Elbird and Paar use Field Programmable Gate Array (FPGA) , encryption rate 4Gbit/s • Can be implemented in satellite TV, HDTV**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Symmetric Encryption • The Serpent Algorithm • Strength: • 32 rounds, probability < 2^-120 • 33 128 bits key • Different rounds use different S-boxes • No weak keys, no semi-weak keys**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Symmetric Encryption • The Serpent Algorithm • Weakness: • Fixed substitution table • Key distribution • Key management**Symmetric Encryption**• The TwoFish Algorithm • Designed by Bruce Schneier, John Kelsey, Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson • block size 128 bits • 128 to 256 bits key length • 16 rounds**Symmetric Encryption**• The TwoFish Algorithm • Split plaintext into 32-bit words • Input whitening: • XORed with four words of key • 16 rounds • Output whitening**Symmetric Encryptoin**• The TwoFish Algorithm • Hardware: • Smart Card • Very-large-scale integration (VLSI)**Symmetric Encryptoin**• The TwoFish Algorithm • Strenght: • 1-bit rotation • no Equivalent key • lacks simplicity**Symmetric Encryptoin**• The TwoFish Algorithm • Weakness: • vulnerable to divide-and-conquer attack of the key space. • lacks simplicity • Key distribution • Key management**Outline**• A Brief History of Cryptography • Symmetric Encryption • Asymmetric Cryptography • Politics in Cryptography • Quantum Cryptography • Summary**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • First proposed in 1976 • "New Directions in Cryptography" Diffie and Hellman • Proposed Public Key encryption • Did not produce an algorithm • Discussed Digital Signatures • Outlined a method of key exchange**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • The RSA Algorithm • “A Method for Obtaining Digital Signatures and Public-Key Cryptosystems” published in 1978 • Proposed by Rivest, Shimar, and Adleman • Called RSA after the authors • Used a computationally difficult problem • C = Me( mod N ) • Breaking requires factoring of large numbers**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • The Elgamal Algorithm • "A public key cryptosystem and a signature scheme based on discrete logarithms" -- 1985 • Proposed by Taher Elgamal • More accurately followed Diffie-Hellman's suggestion • Key Exchange • Digital Signatures • Based around discrete logarithms • C = ek mod p • Better mathematical foundation than RSA**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • RSA being first... • Was used for all public key applications • Secure Socket Layer (SSL) • Pretty Good Privacy (PGP) • Elgamal later... • Replaced RSA in PGP • Better implementation of Diffie-Hellman • Key exchange • Signatures**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • RSA vs. Elgamal • RSA uses longer keys • Elgamal creates longer cipher text • RSA encryption less computationally intensive • Elgamal completely open • RSA key creation very computationally intensive • Elgamal based on better math • RSA offers less security per bit • Elgamal uses evanescent (ephemeral) keys**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • The present • RSA still used for ssl • SSL Requires few key generations • Elgamal • Selected as the Digital Signature Standard (DSS) • Replaced RSA as default in PGP • Implementation of PKI • Public Key Infrastructures (PKI) becoming popular • Generally uses RSA • Provides secure communications across networks**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • The Future • Continued deployment of PKI • Development of Elliptic Curve algorithms • Still theoretical • Already allowed for in standards**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Asymmetric Cryptography • The Problems • Not provably secure • Considered computationally secure • Will require larger and larger keys • Increasing computational power • Theoretical attacks possible • RSA bad key generation • Quantum computing • Will probably obsolesce public key technology • Easy factoring of large numbers**Outline**• A Brief History of Cryptography • Symmetric Encryption • Asymmetric Cryptography • Politics in Cryptography • Quantum Cryptography • Summary**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • Introduction • The National Security Agency • NSA influence • Government export control on cryptography • Current crypto-political status**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • Introduction • World War II - Cryptography major force • Cryptography - Government strictly regulates public development and deployment • 1970s - No big issues with government control over cryptography until 1970s and DES**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • National Security Agency (NSA) • Officially established on December 9, 1952 • President Harry Truman authorizes creation • Agency in the Department of Defense • Purpose to monitor international communications enhance US security • Must use cryptanalysis to read intercepted messages**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • NSA (Continue) • Highly secretive • Believed to be largest employer of mathematicians and cryptographers in the world • Publicly or commercially developed cryptographic materials must be approved by the NSA before export or publication**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • NSA Influence • Data Encryption Standard (DES) • 1972 - 1975 • IBM winning algorithm sent to NSA • NSA “suggested” 2 changes: • Changes to substitution boxes (“s-boxes”) • Key length reduced from 128 bits to 56 bits • Trap-door fear**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • NSA Influence • Khufu and Khafre block ciphers • 1989 • Ralph Merkle, current Georgia Tech professor • Request to publish papers denied by NSA • Copies sent to John Gilmore • Gilmore published the papers on a newsgroup • NSA miffed, but no legal action**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • NSA Influence • Pretty Good Privacy (PGP) • 1991 • Phil Zimmerman • Released PGP to the public on the Internet • NSA and government criminally investigate Zimmerman and battle him in court • In 1996, government drops case and result is seen as victory for computer industry**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • Government Export Control • Cryptography classified as “munitions” • Joint export control by 2 US Departments • Department of State • Handles most cryptography export regulations • Department of Commerce • Jurisdiction over technology exports • Concedes issues involving crypt. to State Dept. • Key length limited to 40 bits (until recently)**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • Government Export Control • Applied Cryptography Case • 1994 • Phil Karn vs. government export laws • Applied Cryptography by Bruce Schneier • Book exportable, but floppy disk not • Case dropped in 2000 • Due to a new law relaxing export regulations**Outline**• History • Symmetric • Asymmetric • Politics • Quantum • Summary Politics and Cryptography • Current Crypto-Political Status • In 2000, Dept. of Commerce relaxed cryptography laws • Publicly available source code freely exportable • Custom cryptographic software still requires a license for export • Exportable everywhere (except 7 nations)**Outline**• A Brief History of Cryptography • Symmetric Encryption • Asymmetric Cryptography • Politics in Cryptography • Quantum Cryptography • Summary