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!

AoC 2017 Day 4: Password Validator

2017-12-04

Source: High-Entropy Passphrases

Part 1: Given a list of passphrases, count how many contain no duplicate words.

AoC 2017 Day 3: Spiraly

2017-12-03

Source: Spiral Memory

Part 1: Create a grid in a spiral pattern like so:

17 16 15 14 13 18 5 4 3 12 19 6 1 2 11 20 7 8 9 10 21 22 23—> …

AoC 2017 Day 2: Check It

2017-12-02

Source: Corruption Checksum

Part 1: The checksum of a list of numbers is the difference between the largest and smallest number in the row. What is the sum of checksums of a file containing many such lists?

AoC 2017 Day 1: Ahctpat

2017-12-01

Source: Inverse Captcha

Part 1: Given a number, what is the sum of pairs of digits that match (wrapping the last digit around to the first)?

AoC 2017: Library Functions

2017-12-01

As mentioned in the main post, I’m structuring my solutions a bit differently this year. Rather than repeating the same relatively lengthy header in each function, we’re going to have a few shared files that can be imported or used for every problem.

Clock drift in Docker containers

2017-11-15

I was working on a docker container which uses the aws cli to mess around with some autoscaling groups when I got a somewhat strange error:

A client error (SignatureDoesNotMatch) occurred when calling the DescribeAutoScalingGroups operation: Signature not yet current: 20171115T012426Z is still later than 20171115T012420Z (20171115T011920Z + 5 min.)

Hmm.

Are the clocks off?

AoC 2016 Day 25: Assembunny3

2016-12-25

Source: Clock Signal

Part 1: Take the assembunny interpreter from day 12 and add one new instruction (out x) which transmits the value x (either an integer or register). Find the lowest value we can initialize a to so that the output signals form an infinite repeating pattern of 0, 1, 0, 1, …

AoC 2016 Day 24: Venti

2016-12-24

Source: Air Duct Spelunking

Part 1: Given a map of the form:

########### #0.1…..2# #.#######.# #4…….3# ###########

AoC 2016 Day 23: Assembunny2

2016-12-23

Source: Safe Cracking

Part 1: Take the assembunny interpreter from day 12 and add an instruction (tgl X) that modifies the code at an offset of X instructions.

inc becomes dec; any other one argument instruction (including tgl) becomes inc
jnz becomes cpy; any other two argument instructions become jnz
Toggling an instruction outside of the program does nothing (it does not halt execution)
If toggling produces an invalid instruction, ignore it

Run the given program with the initial register of a = 7. What is the final value in register a?

AoC 2016 Day 22: Data Mover

2016-12-22

Source: Grid Computing

Part 1: You are given a grid of nodes and the output of the df command telling you how much space is on each. How many pairs of nodes are there where the data from some node A would fit entirely on B?