Delivery McGee posted:

The various intelligence agencies now run ARGs for recruiting purposes -- if you crack the codes, you get offered a job interview -- but as for the codes actually used for sensitive stuff, it's been nigh-impossible for at least most of the last century and getting harder by the minute.

Early codes like Caesar and Washington and Wellington used, the ones that are in puzzle books/Boy Scout "introduction to codes" these days, are fairly simple, but nowadays the ones used by the public (such as the crazy poo poo going on behind the "https" up there in your address bar) are effectively uncrackable; it'd be easier/quicker/cheaper by several orders of magnitude to mine Bitcoins, trade them cash, launder the money to hell and back, buy gold, and use the gold to buy the decryption algorithm off a corrupt NSA agent.

And it's fair to assume the government (at least the NATO/Commonwealth countries and Russia; the government of the week in, say, Somalia probably isn't as sophisticated) are using something two generations ahead of what the public have access to now.

Hell, the WWII German Enigma machine was like banging two rocks together in comparison to what we have now, and it was only shoddy user practices that allowed the Allies to crack it. The users were told its code was unbreakable so they got lazy with changing up the settings, providing the Poles and Brits with enough messages with the same settings to allow standard cryptographic analysis (with the help of the first computers in the modern sense). So the Nazis changed the design and enforced proper practice, which worked until the Brits captured a couple of U-boats and weather-monitoring ships before they could trash the radio rooms, getting a couple of complete machines and sets of codebooks/instruction manuals, and managed to come up with plausible enough alternate explanations for their press releases (which the Germans were reading, of course) announcing the Royal Navy laying waste to this or that wolfpack of U-boats so that Gerry thought his code was still secure and it was just that damned ASDIC and British luck (similarly, the myth about eating lots of carrots making your night vision better was the cover story for British night-fighter pilots to avoid giving away the fact that they had radar).

And all the really fun stuff is encrypted using one-time pads, which are completely random matrices; pretty much the only way to crack a one-time pad before the heat death of the universe is to capture a person using it before they have a chance to destroy their copy of the pad.