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Could we use permutation polynomials for Shamir's secret sharing scheme?

ua flag

Could we use permutation polynomials for secret sharing scheme like Shamir's? The say that they induce a bijection over $\mathbb{Z}_p$ what does this mean and how does it helps?

Score:2
sa flag

Short answer: No

A permutation polynomial is a polynomial $f:\mathbb{Z}_p\rightarrow\mathbb{Z}_p$ which is a bijection meaning the list $[f(x): x \in \mathbb{Z}_p]$ is a permutation of the elements of the field.

Example: For example $f(x)=x^3$ gives the list $[0,1,3,2,4]$ as $x$ ranges over $\mathbb{Z}_5$.

But these polynomials leak information since if you know $(x_0,f(x_0))$ you know for all $x\neq x_0$ the value of $f$ is different than $f(x_0)$.

This means that the Shamir argument about the polynomial values being uniformly distributed if some $s$ shares for $<s<t$ are known no longer holds. Here $t$ is the threshold.

So, no need to do this it introduces a weakness.

Hunger Learn avatar
ua flag
thank you very much!
kelalaka avatar
in flag
In short, it is no more perfect secrecy.
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