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The Manual One-Time Pad

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Re: The Manual One-Time Pad

#11

Post by Karunamon »

ekyepyaport wrote: post #3
sarciszewski wrote: post #2

Though the article says "One-time pad is not a practical encryption system. However, if properly used, it will be absolutely secure and unbreakable", I've had to talk developers out of wanting to implement them in their protocols before. Quick public service announcement about cryptography. It's true that, from an information theory perspective, OTPs are unbreakable encryption. However, unless you have a long history…

I agree, people shouldn't really try to enjoy their hobbies. They should just do what everybody tells them. Imagine if a bank were to accidently mistake your OTP implementation as a viable product. Oh, the humanity.

A bank? No. Some random person out there in an oppressive government? Infinitely more likely.

Crypto is a bit of a special case in programming in that's it's ridiculously easy to do wrong, and failures could have catastrophic consequences on people's real lives. If you want to play with it yourself, more power to ya, but for the love of all things good in the world don't put it out there without sufficient disclaimer that it's a hobby, untested project.

Re: The Manual One-Time Pad

#13

Post by _fizz_buzz_ »

DanielBMarkham wrote: post #9
sarciszewski wrote: post #2

Though the article says "One-time pad is not a practical encryption system. However, if properly used, it will be absolutely secure and unbreakable", I've had to talk developers out of wanting to implement them in their protocols before. Quick public service announcement about cryptography. It's true that, from an information theory perspective, OTPs are unbreakable encryption. However, unless you have a long history…

Speaking as a total novice, I've always found OTPs attractive. Wish you had made a better argument here, for perhaps I'm missing it. Yep, key management is a problem. That's all I got, and I know there had to be more. Do you know of any longer treatments of this subject? Sure would love to read them. I mean, I'm thinking if I want to share data with a friend, I get a hardware true RNG, cut a couple of 1TB SSDs full o…

Here is the thing, the cryptography is really not the weak part of a communication system. You really don't gain anything by using a one-time pad over something like AES-256 in any practical sense. You're only making the part of your system stronger that is already more than strong enough (From a thermodynamics point of view you couldn't even brute force AES-256 if you had a supernova as an energy source [1]). Difficult parts of a secure communication system are authentication, key-exchange, etc.

Example how to compromise your system: I send your friend a message with some random data and pretend to be you. Now he doesn't know what's going on and you two are out of sync and cannot securely re-sync your keys without meeting up again.

[1] https://www.schneier.com/blog/archives/2009/09/the_doghouse_...

Re: The Manual One-Time Pad

#14

Post by sarciszewski »

ekyepyaport wrote: post #3
sarciszewski wrote: post #2

Though the article says "One-time pad is not a practical encryption system. However, if properly used, it will be absolutely secure and unbreakable", I've had to talk developers out of wanting to implement them in their protocols before. Quick public service announcement about cryptography. It's true that, from an information theory perspective, OTPs are unbreakable encryption. However, unless you have a long history…

I agree, people shouldn't really try to enjoy their hobbies. They should just do what everybody tells them. Imagine if a bank were to accidently mistake your OTP implementation as a viable product. Oh, the humanity.

http://www.cryptofails.com/post/75204435608/write-crypto-cod...

Re: The Manual One-Time Pad

#15

Post by sarciszewski »

DanielBMarkham wrote: post #9
sarciszewski wrote: post #2

Though the article says "One-time pad is not a practical encryption system. However, if properly used, it will be absolutely secure and unbreakable", I've had to talk developers out of wanting to implement them in their protocols before. Quick public service announcement about cryptography. It's true that, from an information theory perspective, OTPs are unbreakable encryption. However, unless you have a long history…

Speaking as a total novice, I've always found OTPs attractive. Wish you had made a better argument here, for perhaps I'm missing it. Yep, key management is a problem. That's all I got, and I know there had to be more. Do you know of any longer treatments of this subject? Sure would love to read them. I mean, I'm thinking if I want to share data with a friend, I get a hardware true RNG, cut a couple of 1TB SSDs full o…

> Wish you had made a better argument here, for perhaps I'm missing it.

I did have a better argument here. It was point 2.

Unauthenticated encryption is dangerous:

https://paragonie.com/blog/2015/05/using-encryption-and-auth...

Re: The Manual One-Time Pad

#16

Post by ryacko »

_fizz_buzz_ wrote: post #13
DanielBMarkham wrote: post #9

Earlier quoted context omitted.

Speaking as a total novice, I've always found OTPs attractive. Wish you had made a better argument here, for perhaps I'm missing it. Yep, key management is a problem. That's all I got, and I know there had to be more. Do you know of any longer treatments of this subject? Sure would love to read them. I mean, I'm thinking if I want to share data with a friend, I get a hardware true RNG, cut a couple of 1TB SSDs full o…

Here is the thing, the cryptography is really not the weak part of a communication system. You really don't gain anything by using a one-time pad over something like AES-256 in any practical sense. You're only making the part of your system stronger that is already more than strong enough (From a thermodynamics point of view you couldn't even brute force AES-256 if you had a supernova as an energy source [1]). Diffic…

You can bruteforce AES-256 if you were using a quantum computer.

Or if there's a new advance in algebraic cryptanalysis.

Re: The Manual One-Time Pad

#17

Post by _fizz_buzz_ »

ryacko wrote: post #16
_fizz_buzz_ wrote: post #13

Earlier quoted context omitted.

Here is the thing, the cryptography is really not the weak part of a communication system. You really don't gain anything by using a one-time pad over something like AES-256 in any practical sense. You're only making the part of your system stronger that is already more than strong enough (From a thermodynamics point of view you couldn't even brute force AES-256 if you had a supernova as an energy source [1]). Diffic…

You can bruteforce AES-256 if you were using a quantum computer. Or if there's a new advance in algebraic cryptanalysis.

> You can bruteforce AES-256 if you were using a quantum computer.

Not true. AES does not suffer from the same weaknesses as many public key schemes. A quantum computer could speed up an attack on AES, but does not fundamentally break it.

> Or if there's a new advance in algebraic cryptanalysis.

Sure. But my point was that there are much weaker points than the encryption in a communication system.

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