quartz/content/notes/07-cryptography-applications.md
2022-08-16 13:55:13 +12:00

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---
title: "07-cryptography-applications"
aliases:
tags:
- comp210
- lecture
sr-due: 2022-08-19
sr-interval: 3
sr-ease: 250
---
interest doesn't have low level security
- this would decrease compatibility
- easier to add this at hosts and software layer
# Layer model
- each layer of network hides information about lower levels and adds information for higher levels\
- transmission is only at physical layer
OSI model - more complicated but most common
TCP model
- application (http etc)
- transport (tcp etc)
- network (IP)
- data link (ethernet, wifi)
- physical layer
# End to end principle
- add "smarts" at the endpoints
- easier to change these than the middle
- keep middle simple, scalable, dumb
- KISS
# security not built in
- originall no security
- security was added
- http -> https
- ssl (secure socket layer) has been replaced by tls
- tls (transport layer security)
- ftp - sftp (file transfer)
- scp (secure copy)
- ssh (secure shell)
# security certificates
- client needs to authenticate the server
- also vice versa
- need to establish secure connection
- trusted third parties are used to sign server host's certificates
- "tree of trust"
- based on public key crypto
# GPG
GNU privacy gurad (free libre open source) work alike for PGP
![GPG example|400](https://i.imgur.com/9f2TJl2.png)
# S/MIME
cryptography for email
secure multipupose internet mail expensions
often not used, as it is not usually built in
# Crypto