vault backup: 2022-08-16 13:10:13

content/notes/06-hashing-binary-public-key-cryptography.md

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+---
+title: "06-hashing-binary-public-key-cryptography"
+aliases: 
+tags: 
+- lecture
+- comp210
+sr-due: 2022-08-19
+sr-interval: 3
+sr-ease: 250
+---
+
+# news
+- pegasus project
+- cutting internet cables
+
+# Hash function
+- yields a small, districtive value (hash or digest) from an arbitrarily sized input.
+- one way function
+	- non-invertable
+- uniform size (each ouput eqaully likely)
+- deterministic (same input maps to same output)
+- possibility of collisions (b-day paradox, potential attacks)
+
+message => hash() => hash
+
+also
+- can be used for data structures
+	- [hash-map](notes/hash-map.md)
+	- lots of theory
+	- often use modular arithmetic
+	- usually have more complicated algorithms than mod
+
+## in crypto
+- needs to be
+	- impossible to reverse
+	- difficult to find collision
+	- uniform length output (tunable)
+	- must account for every bit of information in a message
+	- must be sensitive to changes input (avalancge effect)
+	- ouput should no contain apparent iinformation (appears random)
+	- easily computed (usually)
+		- for passowords should be slow
+		- makes brute force attacks take time
+		- key strechting (repeated application of hash)
+		- use complex memory access patterns to defeat esp
+
+effectively a digital fingerprint;
+
+## collision probability
+
+$v = a^l$
+
+- ![theory slide|400](https://i.imgur.com/EqydQtI.png)
+- ![example slide|400](https://i.imgur.com/xEKxhIT.png)
+- ![reverse example slide|400](https://i.imgur.com/eWjhqjv.png)
+
+can also be used to compare complexity of passwords
+- ![passwords slide](https://i.imgur.com/GdaMF4r.png)
+- should have about 80 bits of entropy
+
+
+- ![collision probability slide|400](https://i.imgur.com/auwVphr.png)
+
+## uses of hashing
+![hashing security appplications slide|400](https://i.imgur.com/v5T9yTB.png)
+
+
+# Binary
+
+
+# One-time-pads
+
+
+## limitations
+
+
+# assymetric cryptography
+
+
+# digital signatures
+

content/notes/comp-210.md

@@ -30,3 +30,4 @@ No final exam
 - [03-threats-social-engineering-and-failures](notes/03-threats-social-engineering-and-failures.md)
 - [04-authentication-authorisation-passwords](notes/04-authentication-authorisation-passwords.md)
 - [05-cryptography](notes/05-cryptography.md)
+-