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chrrox, posted Wed Jul 28, 2021 12:54 am (65388)

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is there a way to generate a xor pad fast in qickbms.
it starts at 0 and keeps going higher till the size of the file every 16 bytes like this.

aluigi, posted Fri Jul 30, 2021 5:34 am (65410)

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Fast? uhmmm no.
It depends by how long it should be your xor pad, if it has a limited short size you can build it by hand but if that is supposed to be unlimited (as I think) then it's complicated.

chrrox, posted Fri Jul 30, 2021 11:51 am (65413)

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fastest way would be initialize as 0 the file size then use c program to modify values?

aluigi, posted Fri Jul 30, 2021 3:07 pm (65416)

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A C function for performing the decryption would be good.
Do you mean something like the following?

Code:

set MEMORY_FILE10 string "
void decrypt(unsigned char *data, int size) {
    int i, c;
    for(i = 0; i < size; i  ) {
        c = i >> 4;
        switch(i & 15) {
            case 0:            break;
            case 1:  c >>= 8;  break;
            case 2:  c >>= 16; break;
            case 3:  c >>= 24; break;
            default: c = 0;
        }
        data[i] ^= c;
    }
}
"

get SIZE asize
log MEMORY_FILE 0 SIZE
calldll MEMORY_FILE10 decrypt tcc RET MEMORY_FILE SIZE
log "dump.dat" 0 SIZE MEMORY_FILE

chrrox, posted Fri Jul 30, 2021 8:55 pm (65418)

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That worked great