Petya ransomware - supplied key encoder

petya_encoder.cpp

bool encode(char* key, BYTE *encoded)
{
    if (!key || !encoded) {
        printf("Invalid buffer\n");
        return false;
    }
    size_t len = strlen(key);
    if (len < 16) {
        printf("Invalid key\n");
        return false;
    }
    if (len > 16) len = 16;

    int i, j;
    i = j = 0;
    for (i = 0, j = 0; i < len; i++, j += 2) {
        char k = key[i];

        encoded[j] = k + 'z';
        encoded[j+1] = k * 2;
    }
    encoded[j] = 0;
    encoded[j+1] = 0;
    return true;
}