I don't recall when I first became interested in cryptography, and the mysteries of secret codes and ciphers. Perhaps Sherlock Holmes, The Adventure of the Dancing Men? At any rate, by the time I was into junior high, I was very much into cryptography. I remember friends and I used to swap encrypted messages to see if the other person could crack the cipher— I had a fair amount of success unraveling simple substitution ciphers, and at one time I had the percentage frequencies of the letters of the alphabet for English (ETAOIN SHRDLU...) memorized.
Simple letter substitution. Transposition ciphers. I soon got into the Vigenère cipher, with its 26x26 alphabetic grid: several of my friends and I had our own secret spy organization, and we used a Vigenère cipher with a long phrase in Latin as our keyword.
And eventually I got into other ciphers. For some years my brother and I both carried in our wallets laminated cards with the ADFGVX cipher and the Playfair cipher on them. You understand, the ADFGVX cipher had been seriously used in the field by the German army in World War I, less than 40 years before I was born. And I remember the keyword used to generate my 5x5 Playfair square, a square containing every letter of the alphabet except for J: that keyword was very close to the root password I use in Linux on my computer today.
Cryptography is one of those fields which has advanced light years just within the past generation or two. When I was in junior high, late 1960s, the secret ciphers my friends and I were tinkering with were not long removed from ciphers that had once been seriously used in the real world. But in the decades since then, cryptography has been advancing at a ferocious rate. Computers have had a lot to do with that. I remember the TA who used to have a desk next to mine in the office when we were in graduate school. He later went on to direct some project, computers all over the country coordinated to find large prime numbers for cryptographic (read: national security) use. And of course every time you buy something over the Internet nowadays, your secure connection is employing encryption techniques I never even dreamed of as a boy.
I remember teachers used to discourage us from being interested in cryptography and secret ciphers, as if it was something stupid. (Mrs. Kerr, are you still out there?) There was a lot of that in the culture back in those days, a sour, scowling, narrow negativism, discouraging kids from being inquisitive, in an effort to usher them back into thinking inside the box. Can't allow nonconformity, have to keep the sheep in line, lest the sheep look up and realize the world around them is not so small and narrow after all.
As I look at the world around us today, where a trillion cryptographic flowers have bloomed, I can only smile at the memory of those erstwhile myrmidons of conformity; the best revenge is to have turned out to be on the side of history. The naysayers have been left in the dust. Encryption and cryptography are a vital part of our world today, and they will only continue to advance and grow.
And to think that less than 100 years ago, armies on the battlefield were still using pencil-and-paper secret ciphers whose principles are readily intelligible to schoolchildren.