What does the "x" operator stands for in cryptography? I am studying commitment scheme and in of the notes from the class this statement comes up.


I'd like to know exactly what the X = M x R mean, since I don't seem to understand how the "x" operator should be interpreted in here
$\mathcal X=\mathcal M\times \mathcal R$ simply means that all elements of $\mathcal X$ have the form $(m,r)$ with $m\in\mathcal M$ and $r\in\mathcal R$. So this is an operator that takes two sets and then joins them in a tuple. This is also called Cartesian product.