Secrets from the Future

One of my crypto students pointed me to the "Nerdcore Hip-Hop" group MC Frontalot. Here's a trailer for their tribute film, Nerdcore Rising.

You can download their song Secrets from the Future that makes a good point about the life of crypto. From the (slightly explicit) lyrics

Best of all, your secret: nothing extant could extract it.
By 2025 a children's Speak & Spell could crack it.

You can't hide secrets from the future with math.
You can try, but I bet that in the future they laugh
at the half-a**ed schemes and algorithms amassed
to enforce cryptographs in the past.

I don't expect a general way to break RSA or factor numbers either on classical machines (for lack of algorithms) or quantum machines (for lack of controlled entanglement) in the next couple of decades. Nevertheless you can't count on say a 1024 or 2048 bit RSA key being safe in a decade or two. Better algorithms combined with faster highly parallelized machines may break those codes. Or maybe they won't—but you can't be sure.

Even the NSA gives expiration dates on encrypted data. If you used 100,000 bit keys your secrets should survive into the next century. But you have to wonder—how dark are your secrets that you need them to last?