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Re: Patterns

From William Unruh <unruh@invalid.ca>
Newsgroups comp.security.unix, sci.crypt
Subject Re: Patterns
Date 2024-02-17 00:25 +0000
Organization A noiseless patient Spider
Message-ID <uqoudq$35ch$1@dont-email.me> (permalink)
References (6 earlier) <uqlrlj$2pi12$1@i2pn2.org> <uqmhtl$3ilmr$1@dont-email.me> <uqo45v$2sl5o$1@i2pn2.org> <uqo4p7$2sl5o$2@i2pn2.org> <uqogdn$mfr$1@dont-email.me>

Cross-posted to 2 groups.

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On 2024-02-16, Chris M. Thomasson <chris.m.thomasson.1@gmail.com> wrote:
> On 2/16/2024 9:07 AM, Stefan Claas wrote:
>> Stefan Claas wrote:
>> 
>>> Chris M. Thomasson wrote:
>>>
>>>> On 2/15/2024 12:20 PM, Stefan Claas wrote:
>>>>> Rich wrote:
>>>>>
>>>>>> In sci.crypt Stefan Claas <pollux@tilde.club> wrote:
>>>>>>> Chris M. Thomasson wrote:
>>>>>
>>>>>>>> Or even the other way around? If one knows the OTP (Bob and/or
>>>>>>>> Alice), they can create a special plaintext that generates this
>>>>>>>> output for fun.
>>>>>>>
>>>>>>> How would you do this?
>>>>>>
>>>>>> For a traditional, 1940's substution style OTP, it is trivial:
>>>>>>
>>>>>> Message: The
>>>>>>
>>>>>> Pad:
>>>>>>
>>>>>> T=H
>>>>>> e=r
>>>>>> h=e
>>>>>>
>>>>>> Substitute using the pad, get the encrypted message: Her
>>>>>
>>>>> Well, one uses a substitution table, trigraph, etc. and then
>>>>> a pad to encrypt the message. Otherwise it would be a plain
>>>>> text encoded message, right?
>>>>
>>>> Give me a OPT 3 bytes long. Creating a plaintext that results in a
>>>> ciphertext of say 123, or ABC is possible...
>>>
>>> Yes, but then it is not OTP encryption and only plain code, done
>>> with substitution, I would say. The OP's Subject: is Patterns.
>> 
>> To be more clear, an OTP encrypted message with digits or letters
>> can of course include 3-5 letter words or a 3-5 digits sequence, but
>> in case of OTPs this means nothing and I would not call it pattern,
>> in an encrypted message.
>> 
>
> AFAICT, it all boils down to fun with OTP's... ;^)
>

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.

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Thread

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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