Friday, 23 March 2012
Friday, 16 March 2012
Thursday, 15 March 2012
Nice way to make a sequential number look random
From here: http://stackoverflow.com/questions/611915/obscure-encrypt-an-order-number-as-another-number-symmetrical-random-appea/612085#612085
Useful if you want to use a sequential number as the unique reference for something, but want to obfuscate it so that its non-obvious that its a sequence
Pick a 8 or 9 digit number at random, say 839712541. Then, take your order number's binary representation (for this example, I'm not using 2's complement), pad it out to the same number of bits (30), reverse it, and xor the flipped order number and the magic number. For example:
1 = 000000000000000000000000000001
Flip = 100000000000000000000000000000
839712541 = 110010000011001111111100011101
XOR = 010010000011001111111100011101 = 302841629
2 = 000000000000000000000000000010
Flip = 010000000000000000000000000000
839712541 = 110010000011001111111100011101
XOR = 100010000011001111111100011101 = 571277085
Useful if you want to use a sequential number as the unique reference for something, but want to obfuscate it so that its non-obvious that its a sequence
Pick a 8 or 9 digit number at random, say 839712541. Then, take your order number's binary representation (for this example, I'm not using 2's complement), pad it out to the same number of bits (30), reverse it, and xor the flipped order number and the magic number. For example:
1 = 000000000000000000000000000001
Flip = 100000000000000000000000000000
839712541 = 110010000011001111111100011101
XOR = 010010000011001111111100011101 = 302841629
2 = 000000000000000000000000000010
Flip = 010000000000000000000000000000
839712541 = 110010000011001111111100011101
XOR = 100010000011001111111100011101 = 571277085
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