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43 lines
1.2 KiB
Markdown
43 lines
1.2 KiB
Markdown
---
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title: "cryptography"
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aliases:
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tags:
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- comp210
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---
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Crytography arises from the need for confidentiality. Some people say
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>"if you have nothing to fear you have nothing to hide".
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Edward snowden said
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>"arguing that you don't care about privacy because you have nothing to hide is no different than saying you dont care about free speech because you have nothing to say."
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# History
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One of the earliest known ciphers was the simple subsitution cipher used by julius caesar named the caesar cipher.
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Although it a very bad cipher, it still uses the same general process of encryption and decryption.
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# General Process
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- encrypt
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- plaintext + key => ciphertext
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- key is a secret
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- decrypt
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- ciphertext + key => plaintext
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mathmatically
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- c = e(p, k)
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- p = d(c, k)
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# Randomness
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[randomness](notes/randomness.md) is the basis for the theory of cryptography. The aim of encryption is to alter a message (or binary sequence) so that it is maximally random i.e., has the highest entropy, and to remove any sort of pattern.
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# Terminology/Conventions
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- alice, bob, charlie, etc
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- mallory -> malicious
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- etc
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- public vs private domains
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- assume communication is public
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- assume information is prepared and consumed in private domain
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- copy from lecture 5 slides
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