Re: A simple secret sharing between 2 person

From: b (beshinica_at_yahoo.com)
Date: 06/08/05 

Date: 8 Jun 2005 04:20:18 -0700

tomstde...@gmail.com wrote:
>
> let's re-write your problem in the equivalent but less balanced method
> of
>
> 1. User A gets 127 bits of the block
> 2. User B gets 1 bit of the block
>
> Now user A knows that the plaintext is English ASCII, or an MP3 or an
> MPEG or ...
>
> So he guesses the missing bit and uses the decrypt that makes the most
> sense. Chances are good that only one of them will actually match a
> source language.
>
> What's the point of a secret splitting? The ideal is that with
> unbounded computational time any one [or subset less than threshold]
> party cannot decrypt uniquely the message.
>
> for example, this would be a valid split.
>
> for i = 0 to m-1 do
> 1. T[i] = E_k(i)
> 2. Send P[i] xor T[i] to user A
> 3. Send T[i] to user B
>
> [k = AES key, P = plaintext, m = number of blocks]
>
> Now neither party can decrypt uniquely the text and they have to
> combine the shares to decrypt it.
>
> Tom
The problem with this is that from N input of bits, I get 2*N output (N
for one and N for other).
The method that I described before is that N input of bits is splited
into N/2+N/2 (=N) bits.

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