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content/notes/05-crypography.md

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+---
+title: "05-crypography"
+aliases: 
+tags: 
+- lecture
+- comp210
+---
+
+# news
+- zodiac killer code cracked
+- twitter leak
+
+# Brief history
+- study of secret messages
+- confidentiality of [cia-triad](notes/cia-triad.md)
+- also small role in integrity (authentication of message, and sender)
+- history of cyprtopgraphy is interwined with information technology
+
+Language use for communication seems to be part of human nature: perhaps the use of covert lanuage is too
+
+## need for confidentiality
+"nothing to hide: nothing to fear" look at edward snowdens corrolary
+
+We all have legit needs for privacy. Cryptography provides technical measure for ensuring this privacy.
+
+## history
+- caesar cipher
+	- simple substitution scheme (rotation)
+	- vulnerable to cryptanalysis
+
+# General process
+- encrypt
+	- plaintext + key => ciphertext
+	- key is a secret
+- decrypt
+	- ciphertext + key => plaintext
+
+mathmatically
+- c = e(p, k)
+- p = d(c, k)
+
+# Terminology
+- copy later
+
+# Plaintext
+refers to unencypted message. In the digital age the messages are often not plain text (ascii, unicode, etc).
+
+digital crypto schemes normally work on the binary data (images, .docs, .txt, mp4 etc.)