april 24, 2016 modern physics- nicholas chao 1 · history: classical cryptography pen and paper...

April 24, 2016 Modern Physics- Nicholas Chao 1

Presentation Outline

� What is Cryptography?

� Keys

� Quantum Cryptography


What is Cryptography?

�  “The art of writing or solving codes” � History

� Classical Cryptography � World War II � Modern Cryptography


History: Classical Cryptography

� Pen and Paper � Simple Mechanical Aids

�  The Jefferson Cylinder �  Encrypt and Decrypt Mechanism


History: World War II

� Enigma Rotor Machine �  Alan Turing �  The Imitation Game

� Cryptanalysis �  Breaking of Codes and Ciphers


History: Modern Cryptography

� Keys to Encrypt and Decrypt Information � DES: Data Encryption Standard � AES: Advanced Encryption Standard �  (a) Triple DES Encryption �  (b) Decryption


Keys

� Modern keys are based on mathematics � Keys are strings of bits � Bits

�  0 or 1 �  The more bits, the more possible

combinations � How many possible keys are there for

an 8-bit key?


How keys work

� Algorithm is public knowledge, however, you need a key to get the correct answer.

� Analogy: Lock and key


Public Keys

� Kerckhoff's Principle: All algorithms must be public; only the keys are secret

� How can a key be public? �  Public and private keys


Symmetric vs. Asymmetric

� Symmetric key Algorithm �  All parties must have the same key

� Asymmetric key Algorithm �  Each party has a ○  Public Key ○  Private Key

� Mathematically linked


Symmetric Key Example

� Bob and Alice � Security Issues


Asymmetric Key Example

� Bob and Alice � Computationally

intensive


Quantum Cryptography

� Cryptography using physics � Keys are based on physics, not math

� Quantum Key Distribution �  BB84


Random Numbers

� Generated based on QM physical randomness �  Atomic/Subatomic level ○  Gas molecules bouncing off each other

�  Thermal Noise � Outcome of QM cannot in principle be

predicted �  This is the gold standard of randomness


Quantum Cryptography BB84


Quantum Cryptography Example

� What about Trudy?


Post-Quantum Cryptography

� Quantum Resistance Algorithms � Secure Against Quantum Computers! � Relies on physical properties rather than

mathematics


Conclusion

� History of Cryptography � Symmetric and Asymmetric Keys � Quantum Cryptography


Sources (Page 1) � Bennett, Charles H., Tai Mor, and John

A. Smolin. "ArXiv.org Quant-ph ArXiv:quant-ph/9604040." The Parity Bit in Quantum Cryptography. Phys.Rev. A54, Apr. 1996. Web. 25 Apr. 2016.

� Blumenthal, Matt. "Encryption: Strengths and Weakness." Encryption: Strengths and Weaknesses of Public-key Cryptography (n.d.): n. pag. Web. 20 Apr. 2016.


Sources (Page 2) �  Hjelme, Dag Roar, Lars Lyderson, and

Vadim Makarov. "Quantum Cryptography." SpringerReference (n.d.): n. pag. Arxiv. Arxiv, 7 Aug. 2011. Web. 1 Apr. 2016.

�  Merriam-Webster. Merriam-Webster, n.d. Web. 25 Apr. 2016.

�  "Quantum Cryptography." Wikipedia. Wikimedia Foundation, 21 Apr. 2016. Web. 25 Apr. 2016.


Sources (Page 3)

� Scott, Thomas Jerry. "Cracking Keys with Current Intel CPUs." Cracking Keys with Current Intel CPUs -- Written by Thomas Jerry Scott. Tjscott, n.d. Web. 25 Apr. 2016.

�  Tanenbaum, Andrew S. "Chapter 8." Computer Networks. Upper Saddle River, NJ: Prentice Hall PTR, 1996. 773-76. Print.


Intel Key Cracking Speeds


More about Keys

� Casual: 384-bits (Can be easily broken) � Commercial: 512-bits � Military: 1024-bit (Not breakable by

anyone on Earth) � Alien: 2048-bit (Not breakable by

anyone on other planets)


april 24, 2016 modern physics- nicholas chao 1 · history: classical cryptography pen and paper...

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