hi,
Need help on understanding the following marix
multiplication.
let _ denote subscript.
w=32 bits(0 to 31)
let X be a 32 bit vector
X={X_(w -1),x_(w-2),..x_0}
A=
|1 0 . . |
|0 . |
|. . |
|. . |
|a_(w-1) a_(w-2)....a_0 |
i.e A is an identity matrix w ith last row entries
a_(w-1) a_(w-2)....a_0 which is again a 32 bit vector
We multiply 1*w matrix X with w*w matrix to get a 1*w
matrix as follows
X*A=[X_(w-1)+ X_0*a_*(w-1) , X_(w-2)+
X_(w-2)*a_(w-2),..., X_1+ X_1*a_1 ,
X_0*a_0];
it is said- X*A can be calculated using bit wise
operations as follows
X*A
=
XOR {0 if the least significant bit of
y=0;(multiplying A)
XOR (a if the least significant bit of
y=1;(multiplying A)
how does this hold?
thank you.
Regards Sarath.
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