Programming

The earliest memory I have of ‘programming’ is in the early/mid 90s when my father brought home a computer from work. We could play games on it … so of course I took the spreadsheet program he used (LOTUS 123, did I date myself with that?) and tried to modify it to print out a helpful message for him. It … halfway worked? At least I could undo it so he could get back to work…

After that, I picked up programming for real in QBASIC (I still have a few of those programs lying around), got my own (junky) Linux desktop from my cousin, tried to learn VBasic (without a Windows machine), and eventually made it to high school… In college, I studied computer science and mathematics, mostly programming in Java/.NET, although with a bit of everything in the mix. A few of my oldest programming posts on this blog are from that time.

After that, on to grad school! Originally, I was going to study computational linguistics, but that fell through. Then programming languages (the school’s specialty). And finally I ended up studying censorship and computer security… before taking a hard turn into the private sector to follow my PhD advisor.

Since then, I’ve worked in the computer security space at a couple of different companies. Some don’t exist any more, some you’ve probably heard of. I still program for fun too, and not just in security.

But really, I still have a habit of doing a little bit of everything. Whatever seems interesting at the time!

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AoC 2016 Day 12: Assembunny

2016-12-12

Source: Leonardo’s Monorail

Part 1: Create a virtual machine that has four registers (a, b, c, and d) and can process the following instructions:

  • cpy x y - copies x into y (x can be an integer or a register)
  • inc x - increases register x by one
  • dec x - decreases register x by one
  • jnz x y - jumps over y instructions if x is not zero (x can be an integer or a register)

What is the final value in register a?

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AoC 2016 Day 11: Radiation Avoider

2016-12-11

Source: Radioisotope Thermoelectric Generators

Part 1: Input will be a list of the following form:

  • The first floor contains a hydrogen-compatible microchip and a lithium-compatible microchip.
  • The second floor contains a hydrogen generator.
  • The third floor contains a lithium generator.
  • The fourth floor contains nothing relevant.

You have an elevator that can move exactly 1 or 2 items. You can only leave a microchip on a floor with a non-matching generator if a matching generator is also present.

Move all items to the top (4th) floor.

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AoC 2016 Day 10: Bot Simulator

2016-12-10

Source: Balance Bots

Part 1: Create a sorting machine using input of the following form:

  • value X goes to bot A - an input to bot A
  • bot A gives low to (bot|output) B and high to (bot|output) C - a sorter that takes two inputs and sends them to the specified bots or output channels

Find the bot that compares the values 17 and 61.

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AoC 2016 Day 8: Tiny Screen Simulator

2016-12-08

Source: Two-Factor Authentication

Part 1: Implement a 50x6 pixel screen with the following commands:

  • rect AxB turn on a rectangle of pixels in the top left corner
  • rotate row y=A by B rotates row A right by B pixels
  • rotate column x=A by B rotates column A down by B pixels

After a given sequence of commands, how many pixels are on?

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AoC 2016 Day 4: Room Validator

2016-12-04

Source: Security Through Obscurity1

Part 1: A room is described as a name, a sector ID, and a checksum as follows:

aaaaa-bbb-z-y-x-123[abxyz]

name: aaaaa-bbb-z-y-x sector ID: 123 checksum: abxyz


> A room is valid if the checksum contains the five most common letters if the name (ties broken alphabetically).





An interesting problem. The first thing that we have to do is parse the input:

```python
with open(args.input_file, 'r') as fin:
    for room in fin:
        m = re.match(r'([a-z-]+)-(\d+)\[([a-z]+)\]', room)
        name, sector_id, checksum = m.groups()

        ...

The next thing we want to do is generate a checksum (so we can see if it’s correct):

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