CS 166 tips fleshing out

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 tags: ["SJSU"]
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+A collection of troubleshooting notes, general tips and tricks, or personal thoughts on the CS 166 Information Security class taught by Mark Stamp at SJSU.
+
+Part of this, dealing with specific homework problems, is written with the intention of being a last-resort rescue manual. I only include information you need to get out of potential deep water. No solutions to hard problems. No hand holding, especially no "here is how you solve this problem".
+
+The other part, the tips and thoughts, is just that. I will not stop myself blabbering on for forever.
+
+---
+
+# Recommended Tools
+
+## Hex editor
+I'm only listing two of my favorites here.
+
+HxD <https://mh-nexus.de/en/hxd/>
+
+A very light, Windows-only hex editor. I use it on my laptop for quick things. It definitely will suffice for this class.
+
+ImHex <https://imhex.werwolv.net/>
+
+Much more powerful, but heavier. It has builtin support for pattern matching, processing, disassembly, etc. It also just looks _really really nice_, 200% eye candy factor.
+
+## C compiler
+Some assignments supply C source code that you'll have to compile. In general, they are not compatible with MSVC (Visual Studio), so special care needs taken on Windows.
+
+- macOS: install Xcode Command Line Tools, which contains an Apple-flavored clang. Alternatively, install either clang or gcc from [Homebrew](https://brew.sh/).
+- Liunx: your distro's gcc will do. Or clang if you like that. Honestly if you use Linux why are you even reading this section, go away. :P
+- Windows: install some flavor of gcc
+  - I highly recommend <https://nuwen.net/mingw.html>
+    It’s tiny, just a zip file. Unzip it, you get a `open_distro_window.bat`, which when opened gives you a terminal with everything setup. There is _zero_ room for `PATH` to go wrong.
+  - Otherwise, https://www.msys2.org/
+
+{{< details summary="What's MinGW and what does it have to do with msys2 and cygwin" >}}
+In short, gcc is to MinGW as Linux is to distros.
+
+gcc is a whole bunch of code that can turn C source code, among other things, into an executable. It's designed to run on various \*nix platforms.
+
+MinGW is a bunch of extra code _on top of gcc_ to make it (1) run on Windows, and (2) produce Windows ("PECOFF") executable.
+
+Both projects are just code, they don't provide downloads ("builds"). For gcc, various Linux distros compile them and ship it as a package.
+For MinGW, these projects do the same job:
+
+- https://winlibs.com/
+- https://github.com/niXman/mingw-builds-binaries
+- https://cygwin.com/ \
+  This one tries to emulate the *nix environment on Windows. Comes with quite a few extra programs like bash. _See google._
+- https://www.msys2.org/ \
+  This one builds a whole bunch of softwares in addition to MinGW: bash, make, etc. It's quite complicated, due to those software requring compatibility layers like cygwin to function. I won't explain here. _See google._
+- etc. 
+
+Regardless of which one you download, you get a copy of gcc (and MinGW). The difference is the default configs, and the extra software they ship with gcc.
+
+In fact, you'll hear people call these things "MinGW distros".
+The MinGW project has a [list of notable distros](https://www.mingw-w64.org/downloads/).
+
+I would have linked something instead of writing this myself, but I literally can't find anything of good quality on the internet...
+{{< /details >}}
+
 # Chapter 5
 ## Problem 4 - hash collision
-The expected answer is the square root approximation that’s much glossed over in the textbook, and seen here:
-https://en.m.wikipedia.org/wiki/Birthday_problem#Square_approximation
+Hint: the expected answer _is not_ the exact solution. That's way too complicated
 
-But, for the sake for information, I did end up in quite a rabbit hole trying to find the exact solution. These maybe interesting reads:
+I did end up in quite a rabbit hole trying to find the exact solution. These are not relevant to the textbook at all, but they're still interesting reads:
 - https://math.stackexchange.com/questions/407307/second-pair-of-matching-birthdays
 - https://math.stackexchange.com/questions/2313215/birthday-paradox-2-pairs (same thing, just less general and less verbose)
 - https://math.stackexchange.com/questions/1539271/probability-of-exactly-two-pairs-share-a-birthday-and-each-pair-shares-differen
 
+{{< details summary="More hint" >}}
+It's the square root approximation that’s implied, but much glossed over in the textbook. Fuller explaination here:
+https://en.m.wikipedia.org/wiki/Birthday_problem#Square_approximation
+{{< /details >}}
+
 ## Problem 24 - MD5 collision
 ### I'm getting different hashes
 The messages are supposed to be binary files, but the textbook gave them in hex codes.
 You probably need something like `xxd -r -p`, or [powershell](https://stackoverflow.com/a/64927815), or your hex editor of choice, to turn it into a binary message.
 
+{{< details >}}
 Something like these will work:
 ```sh
 $ cut -d ' ' -f 2- <<'EOF' | xxd -r -p > msg1.bin
@@ -45,6 +107,7 @@ $ md5sum msg1.bin msg2.bin
 ```
 
 FYI, `cut` is used to strip the address column from the string.
+{{< /details >}}
 
 ## Problem 39 - stenography
 ### Getting a blank PDF on windows