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Comment by JKCalhoun | Hacker News Reader

With a one-time pad being, as I understand it, the only really good encryption, I am surprised there is not a market for pairs of matched hard drives—the pair having the same "one time pad" stored on them (how you generate those numbers is left as an exercise for the company marketing them).

A simple app could be used by parties on both ends of the message—an app that relies on an associated drive to act as the pad.

If you become aware that one of the two matched drives has been compromised (stolen perhaps by an outside party), you destroy its partner.

(Perhaps too you can design the drive in such a way as to make it non-trivial to copy—you more or less need possession of the drive itself. That makes it unlikely for there to be a 3rd drive the two parties are unaware of.)

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Conventional symmetric cryptography is already very secure and easy, even in the face of future threats like quantum computers. (Asymmetric cryptography is the type of cryptography that cryptographers spend more time worrying about.) Not that you should do it yourself, but it's relatively easy to whip up a secure symmetric encryption scheme if you have a hash function that meets certain basic security properties (which even hash functions with known weaknesses like MD5 and SHA-1 still meet!). The only real hard part of symmetric cryptography is key management (making sure both ends of each conversation have the matching keys ready to use), and one time pads only make that harder by making the keys very large and stateful. I think there are few use-cases where the potentially increased security makes up for the more difficult key management (especially if it means you're also swearing off all asymmetric cryptography).

the reason why there isn't a market for such drives is that someone who needs that level of security rightfully wouldn't trust any entity to

1. generate truly random data, which is required for OTP to be perfect

2. not store a copy of the data to be handed over to bioluminescent individuals at the drop of a hat

>bioluminescent individuals

Brilliant.

One time pads are the only solution that is secure from an information theoretic perspective. In practice, however, that is not important. You would essentially be securing yourself against a weapon that no one has, and most experts think cannot actually exist.

Russian one time pads were frequently broken. How? They were inconvenient to distribute, so people reused them.

Symmetric cryptography is safer because one key can easily protect as much data as you need.

I would think that a 10TB one-time pad (for example) would probably never get "used up".

I've heard it said that such systems may be used by militaries, where they have an organizational structure naturally-suited to large keystream distribution.

Unlike e-commerce, it's no problem to physically send the proverbial officer handcuffed to a briefcase to the nuclear submarine before it submerges for 6 months.

Also the messages to be secured are, um, short and... infrequent.

I kind of assumed the "customer" here would in fact be government agencies…

I think that post quantum encryption methods might be in this category but I am not knowledgeable enough to say either way.

One issue though with making a one time pad trivial to copy - how do you authenticate that you are allowed to read? How do you know the client isn’t copying?

Surely if you were that security conscious you'd never trust some third party to put the keys on the drives and not keep a copy for themselves - you'd just buy two regular drives and put the key on there yourself.

That's fine. I'm just not aware that even this is being done. But it seems to be pretty secure to being decrypted if captured in transit.

One-time pad has 2 problems:

(1) The key can only be used once. If you use the same key for multiple different messages it's not secure anymore.

(2) The key has to be the same length as the message.

With those 2 restrictions, OTP is not really that feasible for practical applications.

> (1) The key can only be used once.

Sure, and I'm contemplating something like 10 TB of random data as key (I mean hard drives are large these days).

> (2) The key has to be the same length as the message.

I thought that was just a matter of indexing through the (10 TB) of data with each message—picking up in the byte stream where you left off from your previous message.

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