# Meaning of function with circle and cross

I've seen this function M2 = tmp ⊕ Pi. What does the circle with cross do?

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Composition? Unusual notation, but possible . . . Hrm. – 000 Dec 5 '12 at 1:32
In what context did you see this? – copper.hat Dec 5 '12 at 1:36
The article calculated hash functions. tmp is a hash value and Pi is a random secret – einstein Dec 5 '12 at 1:48

In logic and CompSci, $\oplus$ is used to denote the "exclusive or" or "XOR": $\quad x \lor y \land \lnot(x \land y)$.

In set theory, $\oplus$ denotes the disjoint union.

In linear algebra/vector analysis, it's used to denote the direct sum of two vector spaces.

It's also used to denote parity: see P Parity.

Clearly, the context in which it's used is crucial.

In $LaTeX$: use \oplus.

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+1. Educating me for a while now, amWhy! – 000 Dec 5 '12 at 1:51
@Limitless: we're all always learning! – amWhy Dec 5 '12 at 1:55
@Babak Oh no! Weather-related? Something come up? Well, that's a good thing for Math.SE, anyway! (To have you around!) – amWhy Mar 28 '13 at 4:50
@amWhy: My mom didn't want to come for something and that's why It was. Oh yes!. I am here around to help others, any way. :-) – Babak S. Mar 28 '13 at 4:52

$\oplus$ is often used for Directed Sum.

In Computer Science(especially cryptography), $\oplus$ usually means XOR, or bitwise addition.

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Ok I think they meant XOR. Beause the article I read about was about cryptography – einstein Dec 5 '12 at 1:49