2

What do the symbols and mean? I'm trying to understand them to make an app.

It's on http://en.wikipedia.org/wiki/File:XXTEA.png

http://en.wikipedia.org/wiki/File:XXTEA.png

  • 1
    From the context it is obvious that the squared + is simply an addition. – SK-logic Mar 13 '11 at 16:54
  • There's some reference code here, but the single letter variables are giving me a headache. Why does crypto code always look evil to me? – Kevin Jan 12 '15 at 15:18
6

I know for a fact that ⊕ means XOR, or eXclusive OR. With the variables A and B, Normal OR will return true if

  • A=true and b=false
  • A=false and B=true
  • A=true and B=true

XOR on the other hand returns true only if

  • A=false and B=true
  • A=true and B=false

I'm not too sure about ⊞ though. In Unicode its under "SQUARED PLUS", but I don't know how that works in an algorithm

5

I know this is old, but I'll answer the question anyway for future readers:

  • is the XOR function, where two identical bits produce 0, and two different bits produce 1.
  • is a modular addition function, where the modulus must be clearly defined in advance (such as a ⊞ b = a + b mod 2^32).
  • <<n is the left logical bit-shift operator, shifted n-bits (not circular). Left shifting 1-bit would be equivalent to multiplying by 2.
  • >>n in the signed right logical bit-shift operator, shifted n-bits (not circular). Right shifting 1-bit would be equivalent to dividing by 2 and taking the floor of the result.

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