What is XOR?
exclusive or (XOR) 1 , 2
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used in cryptography because it let's us 'flip' the bits using a mask in a reversable operations
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p1 (+) p2 (+) ... (+) pn is true if the number of variables with the value true (1) is odd, because the XOR is associative
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XOR is the same as addition modulo 2
- p1 (+) p2 (+) ... (+) pn == ( p1 + p2 + ... + pn) % 2 - dividing mod 2 is one way to determine if a number is even or odd
- Only the variables that have value 1 contribute to the sum, that determines how many variables have value 1
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doing parity check
- kind of checksum: use the XOR to check whether there is the flip