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# XWIS:APGAR

From ModEnc

APGAR is a token sent by a C&C game to tell XWIS the players' password. The password is encrypted using a weak algorithm. This is a one-way encryption, i.e. you cannot find the original password from it's encrypted form.

Pseudo-code to calculate the password from an 8 letter input:

function apgar(input) lookup = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" out = "" i = 1 while (i <= 8) left = ascii value of input[ i ] right = ascii value of input[ length[input] - i ] if left is odd x = ((left * 2) XOR (left AND 1)) AND right else x = left XOR right out += lookup[x AND 63] i++ return out

A C++ implementation of this algorithm:

std::string apgar(std::string input) { std::string lookup = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; std::string out = ""; int i = 0; while (i < 8) { unsigned char left = input[i]; unsigned char right = input[input.length() - i]; unsigned char x = left & 1 ? ((left << 1) ^ (left & 1)) & right : left ^ right; out += lookup[x & 63]; i++; } return out; }

Example (decrypted password "reneproj"):

apgar Ykbcaxop 0

The closing zero seems to have no special function.