Re: QC-proof cipher?



In article <447a5288.53104415@xxxxxxxxxxxxxxxxxxx>, laura fairhead wrote:
One thing I wonder is people always say this about OTP but what is the
difference between OTP and a NULL cipher. ie; OTP is secure 100% provably
but if and only if your secure channel you trade the key on is 100%
secure, so you could just send your plaintext data down the secure channel
and dummy data (a pdf of applied cryptography say <g> ) down the main
untrusted channel, surely it is the same and thus the OTP is worthless (at
least under that defn. ) ??

You've overlooked a couple things.

First, for many channels, you can detect if someone intercepted the data
(e.g., your courier was beaten up and his package stolen). If you are
sending the key over that channel, then when this happens, you simply don't
use that key. If you were sending plaintext, you are screwed.

Second, there might not be a secure channel at the time you need to send the
message. You don't wait until you need to send a message to send the
key--you send the key long before you have a message. E.g., you give the
key to your submarine commander when he is at base, and then send messages
when he is deployed.

--
--Tim Smith
.



Relevant Pages

  • Re: why dont more password systems use challenge-response?
    ... The other, OTP systems, eliminate the reusable ... > password through that channel - qv SSH, ... For example, SSH and SSL often rely, for creation of their secure channel, ... I can have my account disabled until I get a new card ...
    (comp.security.unix)
  • Re: why dont more password systems use challenge-response?
    ... The other, OTP systems, eliminate the reusable ... > password through that channel - qv SSH, ... For example, SSH and SSL often rely, for creation of their secure channel, ... I can have my account disabled until I get a new card ...
    (comp.security.unix)
  • Re: QC-proof cipher?
    ... difference between OTP and a NULL cipher. ... so you could just send your plaintext data down the secure channel ... If you were sending plaintext, ... well that's true although I think that part of the job of interception ...
    (sci.crypt)
  • Re: QC-proof cipher?
    ... is the difference between OTP and a NULL cipher. ... 100% provably but if and only if your secure channel you trade ... data down the secure channel and dummy data (a pdf of applied ...
    (sci.crypt)