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Transcript of 1 Cryptography Presenter: Group 3 Ahmed Abdalla, Troy Brant, Gabe Campbell, Ana Lim, Saudamini...
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Cryptography
Presenter: Group 3
Ahmed Abdalla, Troy Brant, Gabe Campbell, Ana Lim, Saudamini Zarapkar
Past, Present, and Future
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Outline A Brief History of Cryptography Symmetric Encryption Asymmetric Cryptography Politics in Cryptography Quantum Cryptography Summary
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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
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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
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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.
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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.
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History (continue) Babbage/Kasiski TestCiphertext: 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.
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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.
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History (continue) OneTime 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.
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Outline A Brief History of Cryptography Symmetic Encryption Asymmetic Cryptography Politics in Cryptography Quantum Cryptography Summary
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Symmetric Encryption Overview The Serpent Algorithm The TwoFish Algorithm
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Symmetric (Continue) Overview
DES Invented by IBM In 1976 became an official Federal Information
Processing Standard (FIPS) NIST Effective key length 56bit Double DES, Triple DES
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Symmetric (Continue)
the First AES Conference August 20, 1998 15 candidate algorithms
• 5 US, 10 international
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NIST contest 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
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Symmetric Encryption The Serpent Algorithm
Second place Designed by Ross Anderson, Eli Biham and Lars
Knudsen SubstitutionPermutation Network
• Sboxes: transform input bits into output bits • Pboxes: permute or transpose bits across Sbox inputs.
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Symmetric Encryption The Serpent Algorithm
a block size of 128 bits key length vary from 128 to 256 bits long 33 128bit subkeys 32 rounds
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Symmetric Encryption The Serpent Algorithm
Algorithm:• initial permutation • 32 rounds of Key Mixing, pass through Sboxes,• and linear tranf ormation• a final permutation
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The Serpent AlgorithmOutline History Symmetric Asymmetric Politics Quantum Summary
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The Serpent AlgorithmOutline History Symmetric Asymmetric Politics Quantum Summary
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The Serpent AlgorithmOutline History Symmetric Asymmetric Politics Quantum Summary
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The Serpent Algorithm: Linear Transformation
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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
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Symmetric Encryption The Serpent Algorithm
Strength:• 32 rounds, probability < 2^120• 33 128 bits key• Different rounds use different Sboxes• No weak keys, no semiweak keys
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Symmetric Encryption The Serpent Algorithm
Weakness:• Fixed substitution table• Key distribution• Key management
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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
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Symmetric Encryption The TwoFish Algorithm
Split plaintext into 32bit words Input whitening:
• XORed with four words of key 16 rounds Output whitening
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Symmetric Encryption
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Symmetric Encryptoin The TwoFish Algorithm
Hardware:• Smart Card• Verylargescale integration (VLSI)
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Symmetric Encryptoin The TwoFish Algorithm
Strenght:• 1bit rotation• no Equivalent key• lacks simplicity
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Symmetric Encryptoin The TwoFish Algorithm
Weakness:• vulnerable to divideandconquer attack of the key
space.• lacks simplicity • Key distribution• Key management
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Outline A Brief History of Cryptography Symmetric Encryption Asymmetric Cryptography Politics in Cryptography Quantum Cryptography Summary
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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
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Asymmetric Cryptography The RSA Algorithm
“A Method for Obtaining Digital Signatures and PublicKey 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
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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 DiffieHellman's
suggestion• Key Exchange• Digital Signatures
• Based around discrete logarithms C = ek mod p Better mathematical foundation than RSA
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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 DiffieHellman• Key exchange• Signatures
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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
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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
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Asymmetric Cryptography
The Future Continued deployment of PKI
Development of Elliptic Curve algorithms• Still theoretical
• Already allowed for in standards
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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
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Outline A Brief History of Cryptography Symmetric Encryption Asymmetric Cryptography Politics in Cryptography Quantum Cryptography Summary
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Politics and Cryptography
Introduction The National Security Agency NSA influence Government export control on cryptography Current cryptopolitical status
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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
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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
Politics and Cryptography
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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
Politics and Cryptography
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NSA Influence Data Encryption Standard (DES)
• 1972  1975
• IBM winning algorithm sent to NSA
• NSA “suggested” 2 changes:• Changes to substitution boxes (“sboxes”)
• Key length reduced from 128 bits to 56 bits
• Trapdoor fear
Politics and Cryptography
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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
Politics and Cryptography
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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
Politics and Cryptography
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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)
Politics and Cryptography
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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
Politics and Cryptography
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Politics and Cryptography Current CryptoPolitical 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)
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Outline A Brief History of Cryptography Symmetric Encryption Asymmetric Cryptography Politics in Cryptography Quantum Cryptography Summary
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Quantum Cryptography Introduction to quantum theory Overview of quantum computing Implications of quantum computing on
current encryption algorithms The BB84 Algorithm The E91 Algorithm Limitations and the Future
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Quantum Theory Heisenberg Uncertainty Principle
Certain quantum properties are intrinsically related (ex. position and momentum)
Knowing the exact details of both is impossible• Measuring one introduces some level of
randomness to the other. This will be used in quantum cryptography to
detect interception.
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Quantum Theory Superposition
Before being observed, a particle can exist as the superposition of multiple states.
When the particle is observed, it collapses into only one of those states.
Traditional bits exist as either a 0 or 1. Quantum bits (qubits) can exist in both states
simultaneously.
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Quantum Theory Entanglement
Two or more particles can have properties that are linked, even when they are spatially separated
Ex. Two entangled particles exist with entangled spin (spin can be up or down).
• Measuring the spin on one particle ensures that the other will have the opposite spin.
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Breaking Current Algorithms
Shor's Algorithm is a method for factoring prime numbers and solve discrete logarithms
RSA and Elgamal assume complexity in solving these problems.
Shor's utilizes superposition to evaluate multiple states simultaneously and factor the number in polynomial time.
RSA and Elgamal are theoretically broken.
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Breaking Current Algorithms
DES Grover's quantum search algorithm allows for
enhanced database searching, again using superposition.
This allows for a significantly faster brute for attack on the DES algorithm.
Speed increase is “only” quadratic and increasing key length still provides extra security.
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The BB84 Algorithm Proposed by Bennett and Brassard in 1984. Utilizes the uncertainty principle to ensure
secure quantum key distribution (QKD). Key is based upon polarizations of single
photons sent between source (Alice) and receiver (Bob)
90° for a 0 and 0° for a 1 OR 135° for 0 and 45° for a 1
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The BB84 Algorithm Alice chooses a random string of
bits and random sequence of bases. She sends Bob a train of single photons. Bob measures each photon with a
randomly chosen polarization Bob tells Alice what polarizations he chose. Alice tells Bob which were correct Bob and Alice pick a few random bits to
verify the keys integrity.
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The BB84 Algorithm
What if there was an eavesdropper (Eve)? Eve could only get the polarization correct half
the time and half of those would be measured wrong.
An incorrect choice would destroy the actual information due to the uncertainty principle.
So if Eve measured every bit, he would see an error rate of 25%.
When Bob and Alice compare bits, any inconsistency would indicate Eve's presence.
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Disadvantages of BB84
Need to send exactly ONE photon for each bit. An extra would theoretically allow Eve to
intercept. Lasers this precise are hard and expensive
to produce. Single photon receptors are difficult as well. Susceptible to a specific man in the middle
attack.
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Using Quantum Entanglement Proposed by A. Ekert
in 1991. Similar to the BB84
algorithm, but utilizing entanglement as well as uncertainty.
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The E91 Algorithm A third party or Alice creates a
pair of polarized, entangled photons. The polarization and bit value for each
photon is random. Alice receives one photon, Bob the other. Each measures their photons using random
bases. They exchange which were used. If they
used the same basis, the resulting measurements will be correlated.
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The E91 Algorithm What if ever persistent Eve
eavesdrops again? As before, incorrect measurement of the
photon's value destroys the information. Additionally, should Eve try and generate
photons of her own, checks can be run to be sure the photons were entangled.
Overall more secure than BB84. Main disadvantage is higher cost compared
to BB84.
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Challenges and the Future Challenges
Dedicated fiber run between Bob and Alice High cost of equipment. Implementations still somewhat untested.
Future of QKD Transmission distances are steadily increasing.
Current max is 150km. New algorithms and implementations are being
proposed regularly. Quantum physics developments will continue to
provide more options.
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Summary
History of Cryptography Symmetric Encryption Asymmetric Encryption Political in Cryptography Quantum Cryptography
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Image Sources AJ Elbirt, C. Paar. “An FPGA Implementation and Performance Evaluation of the Serpent Block
Cipher.” The Association for Computer Machinery. International Symposium on Field Programmable Gate Arrays. Pg 3340. 2000.
http://portal.acm.org/citation.cfm?id=329176&coll=portal&dl=ACM A. Poppe, A. Fedrizzi, H. Hübel, R. Ursin, A. Zeilinger, “Entangled State Quantum Key
Distribution and Teleportation”, 31st European Conference on Optical Communication, 2005, pt.
5, 61 vol.5 B. Schneier, J. Kelsey, D. Whiting, D. Wagner, C. Hall, and N. Ferguson. “Twofish: A 128Bit
Block Cipher.” cipher wheel: http://www.practicalturkish.com/ottomanpresentdaycodewheel.jpg SIGABA: http://encyclopedia.quickseek.com/images/Sigaba.jpg
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Questions?