OTP is perfectly secure, but (for many cases) perfectly useless. Transmitting the key safely is exactly as hard as transmitting the message safely.

They're useful in exactly one situation: when you have a temporary secure communication channel, and a long-term insecure channel. Then you can use the temporary channel to pre-share a lot of key material (say, a 1TB micro SD card carried covertly) and then use that for future messages. But that scenario is very rare.

The rarity of that scenario is dictated by there rarely being a need for the security it offers. But that, in turn, is a function of our knowledge of cryptography, and may change over time. Who knows; perhaps someday we'll see something like what Vinge described in AFutD:

"Our main cargo is a one-time cryptographic pad. The source is Commercial Security at Sjandra Kei; the destination is the certificants' High colony. It was the usual arrangement: We're carrying a one-third xor of the pad. Independent shippers are carrying the others. At the destination, the three parts would be xor'd together. The result could supply a dozen worlds' crypto needs on the Net for ..."

Yup, that bit from Fire Upon the Deep is exactly what I was thinking of when I mentioned that bit about industries to safely transmit OTP data.

I don't really think the parent comment understands that there are creative ways around the difficulty of sharing secure pads. We don't need it for all data; but I think Vinge does hint at a totally viable means of sharing, and scenario in which it's practical.

Quantum computing may eventually force us to move to OTPs. Of course it's going to be a pretty long time before we'll have quantum computers that can work across an 800-bit field.

It won‘t. Symmetric ciphers are holding up just fine against quantum computers.

Key exchanges would be annoying, but they are even more so for one-time pads.

But it will never come to even that: There are plenty quantum-safe asymmetric cryptosystems around.

Yeah. I take up the key exchange problem (and Diffie-Hellman) as well as difficulty of achieving true randomness.

I've made matlab scripts that pull true randomness out of the less-significant figures of the output of an audio microphone listening to static...it's not impossible.

If we were serious about it, sharing flash drives and even using couriers could make it work pretty well.