Sometimes when I'm wearing my tinfoil hat I wonder if the advice to avoid rolling your own crypto is a conspiracy. The powers that be want to maintain their backdoors, maybe? Probably not. Of course, it's definitely true that there are more attack vectors out there than an amateur can be aware of.
I think I remember a scifi story that mentioned some character who worked in the one-time-pad shipping business. I guess a spacecraft full of data storage can hold enough random data to last for a long time.
Seems like we should at least come up with a proper protocol for it, so we can at least get started with something that's broadly compatible.
…you're not using a one-time pad. OTP requires the pad to be truly random: at least one bit of unique, never-used-elsewhere entropy for every bit in the message. Merely XORing some plaintext with a pseudo-random stream based on a smaller seed, which as you say is the basis for various other encryption algorithms, is not a one-time pad.
The real problem with OTP is key distribution: You need to share pads with everyone you might want to communicate with, one pad per sender/receiver pair, and those pads need to be at least as large as all the message you'll eventually want to exchange. There is no OTP equivalent to public-key cryptography where you only need one private/public keypair per recipient.
I wouldn't call OTP "fragile" or "hard to use", but you're correct about the key distribution difficulties.
Unless that was a preshared key, you're not talking about a one time pad. One time pads are inherently symmetric. If you're comparing symmetric to assymmetric crypto systems, you might as well just say that 'if my grandmother had wheels, she'd be a bicycle'.
Stream ciphers and OTPs are both symmetric.
The "symmetric" part is the fact that the same key is used for encryption and decryption, not that the plaintext and key are the same length.
> I think I remember a scifi story that mentioned some character who worked in the one-time-pad shipping business.
A Fire Upon the Deep, by Vernor Vinge.
The strength of the system can be viewed from multiple angles. From a practical angle, applying one kind of commercial encryption on top of another type of commercial encryption turns it into a technically weaker, but unique cryptosystem. And uniqueness has value if you're just a single fish in a big pond.
For instance, if one single An0m customer had applied a caesar cypher to their communications, the cops might have skipped over him due to the unknown cost of putting dedicated crypto effort into one person in a massive dragnet.
And since you mentioned Schneier textbook, he also said that a good safe is the one that you give to your adversaries with the blue print of how it's made and still is uncracked, not the one that you dump in the middle of the ocean and ask your adversaries to crack it (security through obscurity).
PGP is still uncracked, if I'd become a criminal then public PGP with at least 8k bits key would be my choice.
It's not PGP that is uncracked, PGP is a set of tools built on top of RSA. RSA is still secure (other than brute force factoring) with appropriately sized keys.
The biggest problem with PGP isn't PGP itself, it's your opsec approach to everything else. Example... after decrypting a PGP payload - did you save it to disk unencrypted? Did the recipients to your messages save it unencrypted? Are any machines infected with keyloggers? PGP is a great tool, but still requires good opsec overall.
I think that if we are going to be concerned about multiple layers of encryption, as you say, then we should be equally concerned with things such as what encoding we use to send text with, or whether we use gzip or bzip. It would suck having to worry about all that; good encryption algorithms work regardless of how their plaintext is encoded, and home grown encryption is just another form of encoding.