4 ms·

Exactly. And provided that the length of the one time pad is EQUAL TO or BIGGER than the plaintext. But this is not very practical

by Faaak 9y ago

anikain 9y ago
The question was not about usability. It was about secure communication. OTP does provide perfect secrecy
Twotriads 9y ago
As with other forms of encryption, there's still the issue of key management / delivery over a secure channel. If you can't guarantee the pad cannot be intercepted, this method is also insecure...
e12e 9y ago
I don't know. You can easily get sdhc cards that are 128GB, ditto for usb sticks. You'd need a high-bandwidth source of random data - or possibly proxy that with high-quality seed for a stream/bloc cipher (conceivably, it's easier to guarantee a one-time, controlled secure generation of a 256 bit symmetric key that's thrown away after generating your stream, than handling of session keys and complicated calculations on a message by message basis) - but I'm not aware of any secure system designed to work with such a one-time pad. You'd need a way to keep track of sections of the pad [probably framing the message, maybe a start keyword could work - it'd give away the section of the pad, but as that section is never re-used... or, if you can assume few messages will be lost, just keep a local counter, and do a sliding search] - and there are other issues. Split the pad into sender/receiver sections (A only encrypt and send with a-apd, B only encrypts with b-pad - to avoid two messages encrypted with the same section of pad, crossing each other). Still, if Eve gets a hold of a plaintext message from Bob, and can intercept the ciphertext before it gets to Alice - Eve gains access to a section of the otp by xoring - and can send anything to Bob (up to the same message length). I'd be interesting to hear if there are modern cryptosystems /research based around one time pads?
- elcapitan 9y ago
  > I'd be interesting to hear if there are modern cryptosystems /research based around one time pads? There's this implementation from 2015: https://techcrunch.com/2015/03/24/one-time-pads-ride-again/ https://techcrunch.com/2015/03/24/one-time-pads-ride-again/

Exactly. And provided that the length of the one time pad is EQUAL TO or BIGGER than the plaintext. But this is not very practical

by Faaak 9y ago

Exactly. And provided that the length of the one time pad is EQUAL TO or BIGGER than the plaintext. But this is not very practical

anikain 9y ago

The question was not about usability. It was about secure communication. OTP does provide perfect secrecy

Twotriads 9y ago

As with other forms of encryption, there's still the issue of key management / delivery over a secure channel. If you can't guarantee the pad cannot be intercepted, this method is also insecure...

e12e 9y ago

I don't know. You can easily get sdhc cards that are 128GB, ditto for usb sticks. You'd need a high-bandwidth source of random data - or possibly proxy that with high-quality seed for a stream/bloc cipher (conceivably, it's easier to guarantee a one-time, controlled secure generation of a 256 bit symmetric key that's thrown away after generating your stream, than handling of session keys and complicated calculations on a message by message basis) - but I'm not aware of any secure system designed to work with such a one-time pad. You'd need a way to keep track of sections of the pad [probably framing the message, maybe a start keyword could work - it'd give away the section of the pad, but as that section is never re-used... or, if you can assume few messages will be lost, just keep a local counter, and do a sliding search] - and there are other issues. Split the pad into sender/receiver sections (A only encrypt and send with a-apd, B only encrypts with b-pad - to avoid two messages encrypted with the same section of pad, crossing each other). Still, if Eve gets a hold of a plaintext message from Bob, and can intercept the ciphertext before it gets to Alice - Eve gains access to a section of the otp by xoring - and can send anything to Bob (up to the same message length). I'd be interesting to hear if there are modern cryptosystems /research based around one time pads?

elcapitan 9y ago
> I'd be interesting to hear if there are modern cryptosystems /research based around one time pads? There's this implementation from 2015: https://techcrunch.com/2015/03/24/one-time-pads-ride-again/ https://techcrunch.com/2015/03/24/one-time-pads-ride-again/