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Re: Coded sentences

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Am 09.04.2016 um 22:21 schrieb William Unruh:
> On 2016-04-09, Mok-Kong Shen <mok-kong.shen@t-online.de> wrote:
>> Am 09.04.2016 um 00:44 schrieb William Unruh:
>>> On 2016-04-08, Mok-Kong Shen <mok-kong.shen@t-online.de> wrote:
>>>> Am 08.04.2016 um 03:30 schrieb William Unruh:
>>>>> On 2016-04-07, Mok-Kong Shen <mok-kong.shen@t-online.de> wrote:
>>>>>>
>>>>>> A codebook in classical crypto is a mapping from a chosen number of
>>>>>> normal or nonsense words to the corresponding intended words or even
>>>>>> phrases and sentences. Wouldn't a generalization of that idea, namely a
>>>>>> mapping from certain types of sentences to the corresponding intended
>>>>>> phrases or sentences be much more versatile and useful in practice for
>>>>>> purposes of steganographical transmission of secret messages? I mean
>>>>>> e.g. a rather mundane sentence expressing the fact that some friends
>>>>>> came to visit us and we have together done something and that they'll
>>>>>> further travel to somewhere could be written in a quite large number of
>>>>>> different ways textually via varying the names of the visitors and what
>>>>>> we have jointly done etc. as well as via varying the grammatical
>>>>>> constructions of the sentence.
>>>>>
>>>>> If you have 5 words you want to transmit, OK. If you want to encrypt
>>>>> 10^9 bytes, it is hopeless. Languages are pretty well structured, and
>>>>> meaning is also well structured. It is really hard to tell a computer
>>>>> how to manufacture plausible and meaningful text.
>>>>> So no, it would not be more versatile and useful.
>>>>
>>>> I must say that I personally never have dreamed of ever having a need
>>>> to send a message of 10^9 bytes. What I meant is that one could employ
>>>> the idea I sketched to sufficiently well send some short pieces of
>>>> secret messages steganographically. In general it is obvious that
>>>> really high secret messages are invariably short.
>>>
>>> Not obvious at all. The Panama papers were almost certainly sent
>>> encryptoed, and were hardly short. The Snowdon papers the same.
>>>
>>> If you want to do it, go ahead, but I thought that you were asking a
>>> general question not one which just referred to you.
>>>
>>
>> Well, one could certainly find exceptions or at least reasonalble
>> exceptions. I tend to think of situations like the case where a
>> representative of a firm in a negotiation with a customer (under
>> competition of rival firms) needs to question his chief and get
>> instructions from him. I suppose the diverse possible essential
>> questions and answers could be somehow foreseen and so managed to
>> be hidden in innocent messages to prevent the potential risks of
>> espionage.
>
> It is called pgp. You just encrypt your message. No need to anticipate
> the questions beforehand. It can ge used for any possible message you
> would want to send, even unforseen ones.  Why the need for
> steganography. Sure you could agree with your boss that if dogs are
> mentioned int he message you mean yes, and if cats, no.
> But steganography is limited to the rare cases when the fact that you
> are using hiding should not be obvious to anyone, requires lots of
> advance preparation, and is completely obvious unless you are really
> creative in the way you manufacture the message. It is also horrendously
> "expensive" (transmitted text much much much larger than the message to
> be sent).
>
> Note that this type of crypto is ancient. It is also pretty limited in
> its usefulness. Modern crypto means that you do not have to worry about
> your message being readable. No Stego needed.

I don't understand why you want to unconditionally neglect certain 
feasible alternatives which under suitable conditions could be useful.
Analogy: If you have a motorcycle, you can from your home extremely
fast reach any arbitrary point of your city. But in some cases riding
a bicycle may be just as fine and perhaps also more enjoyable, though
the radius of reachability is for practical reasons comparatively
limited and it takes more time to get to your destinations.

M. K. Shen

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Coded sentences Mok-Kong Shen <mok-kong.shen@t-online.de> - 2016-04-07 22:36 +0200
  Re: Coded sentences William Unruh <unruh@invalid.ca> - 2016-04-08 01:30 +0000
    Re: Coded sentences Mok-Kong Shen <mok-kong.shen@t-online.de> - 2016-04-08 23:14 +0200
      Re: Coded sentences William Unruh <unruh@invalid.ca> - 2016-04-08 22:44 +0000
        Re: Coded sentences Mok-Kong Shen <mok-kong.shen@t-online.de> - 2016-04-09 19:54 +0200
          Re: Coded sentences William Unruh <unruh@invalid.ca> - 2016-04-09 20:21 +0000
            Re: Coded sentences Barry Margolin <barmar@alum.mit.edu> - 2016-04-09 16:31 -0400
            Re: Coded sentences Mok-Kong Shen <mok-kong.shen@t-online.de> - 2016-04-10 23:09 +0200
              Re: Coded sentences William Unruh <unruh@invalid.ca> - 2016-04-10 21:28 +0000
                Re: Coded sentences Mok-Kong Shen <mok-kong.shen@t-online.de> - 2016-04-11 22:39 +0200
                Re: Coded sentences William Unruh <unruh@invalid.ca> - 2016-04-11 21:47 +0000
                Re: Coded sentences Mok-Kong Shen <mok-kong.shen@t-online.de> - 2016-04-12 21:55 +0200

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