how to use a variable in finite field

Question

ling 2024-4-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2103686-how-to-use-a-variable-in-finite-field

回答： Paul 2024-4-6

sym a;

I want y=gf(3,8)*a, but it did not work.

4 个评论
显示 2更早的评论隐藏 2更早的评论

ling 2024-4-6

The polynomial can be easily reconstructed using Lagrange interpolation in GF(p),where p is a primer.

Manikanta Aditya 2024-4-6

Yeah

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

John D'Errico 2024-4-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2103686-how-to-use-a-variable-in-finite-field#answer_1437396

编辑：John D'Errico 2024-4-6

在 MATLAB Online 中打开

g = gf(3, 8)
 
g = GF(2^8) array. Primitive polynomial = D^8+D^4+D^3+D^2+1 (285 decimal)
 
Array elements = 
 
   3
whos g
  Name      Size            Bytes  Class    Attributes

  g         1x1                92  gf                 

g is a gf object. But g is not compatible for multiplication by a symbolic parameter. These are two independent (and unfortunately, incompatible) toolboxes. They don't talk to or with each other. This is why when you do try to multiply g with a symbolic object, it fails.

syms a
g*a
Error using gf
Expected input x to be one of these types:

double, single, uint8, uint16, uint32, uint64, int8, int16, int32, int64

Instead its type was sym.

Error in gf (line 191)
                        validateattributes(x,{'numeric'}, {'integer', ...

Error in gf>areCompatible (line 1481)
if ~isa(b,'gf'), b=gf(b,a.m,a.prim_poly); return; end

Error in * (line 931)
            [x,y]=areCompatible(x,y,'mtimes');

As the error message says, the only things you can multiply a gf object by are in that list of numeric classes. A sym is not one of the allowed classes for that operation.

You could possibly write your own set of tools that would work as you wish, essentially rewriting the gf class. Since a sym can take on any value, and it MUST be discrete for that operation to make any sense at all, it might take some work on your part to do so in a valid way.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Paul 2024-4-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2103686-how-to-use-a-variable-in-finite-field#answer_1437401

在 MATLAB Online 中打开

How about something along these lines?

y = @(a) gf(3,8)*a;
y(1)
 
ans = GF(2^8) array. Primitive polynomial = D^8+D^4+D^3+D^2+1 (285 decimal)
 
Array elements = 
 
   3
y(2)
 
ans = GF(2^8) array. Primitive polynomial = D^8+D^4+D^3+D^2+1 (285 decimal)
 
Array elements = 
 
   6