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Re: Patterns

Cross-posted to 2 groups.

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On 2024-02-17, Rich <rich@example.invalid> wrote:
> In sci.crypt William Unruh <unruh@invalid.ca> wrote:
>> A One Time Pad means what it says. It can only be used once. It must be
>> the same size as the message to be encrypted (ie you cannot use pad from
>> earlier in the message to encode later stuff.) Otherwise it is weak. It
>> is not a substition cypher (eg your T=H e=r h=e ) to encrypt any other
>> occrances of T, h or e. That is NOT an OTP. It is a MRP (Many time pad)
>> which is woefully weak. A OTP is unconditionally secret. It cannot be
>> broken. An MTP is very weak, or a substitiution cypher is very weak
>> unless the substition block is really large. 
>> OTPs are not fun. They are boring, because there is no way they can be
>> broken, unless you capture the key. But of course that is their problem
>> since you have to get the key to the recipient, without the enemy
>> capturing the key, and the key is huge, so hard to hide.
>
> All correct, and also Whoosh!...
>
> The OP (the Doctor, likely trolling as he has not again been seen in 
> this thread) posted a string of sequential letters and numbers and 
> asked what "encryption" was used.
>
> Jacob, in message <uqg2om$252r4$1@dont-email.me> correctly pointed out 
> that /assuming/ it even was an "encrypted" output, that one way to have 
> created the sequential string as the "cipher text" was to specially 
> craft an OTP "pad" for a known message to result in the given output.
>
> Stefan, in message <uqln3h$2pbms$1@i2pn2.org> asked how this could be 
> done.  My reply with the T=H substitution was an extremely simplified 
> explanation of how one could craft a pad to cause a given output to 
> appear.

Take the original encrypted text. Write down ANY text of the same length
as the encrypted text. Now take the bitwise xor of the original with
your test. The result will be a one time pad which could have been used
to encrypt your madeup text. Ie, you have found a one time pad which
would decrypt the original encrypted text to your Any text.
 Of course the probability that your ANY text was what was originally
 encrypted is vanishingly small. (1/2^N) where N is the number of bits
 in the encrypted text. )f course if it were known to be english text
 that was encrypted, the probability is higher (about 1/2^(N/5) I think,
 but that still produces a very very small number, and is probably far
 worse than if you just dream the text that was encrypted)

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Patterns doctor@doctor.nl2k.ab.ca (The Doctor) - 2024-02-13 01:30 +0000
  Re: Patterns Jakob Bohm <jb-usenet@wisemo.invalid> - 2024-02-13 16:44 +0100
  Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-13 12:43 -0800
    Re: Patterns Rich <rich@example.invalid> - 2024-02-14 04:45 +0000
      Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-14 12:22 -0800
        Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-15 20:02 +0100
          Re: Patterns Rich <rich@example.invalid> - 2024-02-15 19:51 +0000
            Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-15 21:20 +0100
              Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-15 18:39 -0800
                Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-16 17:57 +0100
                Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-16 18:07 +0100
                Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-16 12:26 -0800
                Re: Patterns William Unruh <unruh@invalid.ca> - 2024-02-17 00:25 +0000
                Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-16 17:12 -0800
                Re: Patterns Rich <rich@example.invalid> - 2024-02-17 05:39 +0000
                Re: Patterns William Unruh <unruh@invalid.ca> - 2024-02-18 21:04 +0000
          Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-20 13:09 -0800
            Re: Patterns Richard Harnden <richard.nospam@gmail.invalid> - 2024-02-20 21:55 +0000
              Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-20 14:15 -0800
                Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-20 14:17 -0800
              Re: Patterns doctor@doctor.nl2k.ab.ca (The Doctor) - 2024-02-20 22:17 +0000
            Re: Patterns William Unruh <unruh@invalid.ca> - 2024-02-20 23:47 +0000
            Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-21 19:24 +0100
              Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-22 16:21 -0800
                Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-23 15:00 +0100
                Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-23 19:59 +0100
                Re: Patterns "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-02-23 12:23 -0800
                Re: Patterns Stefan Claas <pollux@tilde.club> - 2024-02-24 20:25 +0100

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