I used to spy on my brother.

Kresten was six years older than me, he had his own room, a yellow Sony Walkman, and a bike with 18 gears. If you ever had an older brother like mine, you know that Kresten was a God, and his room a forbidden realm of magic and mystery.

On one of my expeditions into this realm, I found treasure. Sheets filled with jumbled up letters, numbers and arcane-looking symbols arranged into groups of five. An alien language! I knew the letters were from our cousin, who was widely considered a math prodigy; who knew what delicious secrets were hidden in those pages?

I had to know.

The school library had a book on cryptography, and I devoured it. Armed with my new knowledge of ciphers and their weaknesses, I returned to the mysterious scripts. The first substitution cipher fell easily to the frequency analysis and chosen-plaintext attacks from the book. First “e”, then “r”, and so on, each deciphered letter revealing more of the hidden message until my brother's secrets were mine.

My inevitable gloating at cracking my brother's simple cipher only made my nemesis escalate to ever more complex ones: Caesar, Vigenère, Ottendorf, Alberti. One by one, I would learn their weaknesses and crack them. What was in the letters no longer mattered. I was hooked. I was Alan Turing at Bletchley Park. I was eight, and I had discovered cryptanalysis.