KTK3 savefile analysis

It's a bit frustrating when I Wanna Kill The Kamilia 3 (IWKTK3) savefile have some sort of machine-binding mechanism in place and I can't find any information about it. So here you go.

Fields

All the following fields are random numbers generated on first launch.

registry_set_root(0);
if (registry_exists_ext("kmi", "ID")) {
    global.field90 = registry_read_real_ext("kmi", "ID");
} else {
    global.field90 = irandom(899999) + 100000;
    registry_write_real_ext("kmi", "ID", global.field90);
}
registry_set_root(0);
if (registry_exists_ext("kmj", "DT")) {
    global.field85 = registry_read_real_ext("kmj", "DT");
} else {
    global.field85 = irandom(899999) + 100000;
    registry_write_real_ext("kmj", "DT", global.field85);
}
registry_set_root(0);
if (registry_exists_ext("kmj", "CR")) {
    global.field687 = registry_read_real_ext("kmj", "CR");
} else {
    global.field687 = irandom(899999) + 100000;
    registry_write_real_ext("kmj", "CR", global.field687);
}

global.field90: \\HKCU\kmi\ID
global.field85: \\HKCU\kmj\DT
global.field687: \\HKCU\kmj\CR

Validation

DeathTime:

#define script29
var field82, field83, field84;
if (file_exists(working_directory + "/Data/DeathTime") == 1) {
    field82 = file_bin_open(working_directory + "/Data/DeathTime", 0);
    field83 = file_bin_read_byte(field82) * 100000;
    field83 += file_bin_read_byte(field82) * 10000;
    field83 += file_bin_read_byte(field82) * 100;
    field83 += file_bin_read_byte(field82);
    if (field83 != global.field85) {
        show_message("Wrong Savefile!");
        game_end();
        exit;
    }
    global.field25 = file_bin_read_byte(field82) * 1000000;
    global.field25 += file_bin_read_byte(field82) * 10000;
    global.field25 += file_bin_read_byte(field82) * 100;
    global.field25 += file_bin_read_byte(field82);
    global.field86 = file_bin_read_byte(field82) * 1000000;
    global.field86 += file_bin_read_byte(field82) * 10000;
    global.field86 += file_bin_read_byte(field82) * 100;
    global.field86 += file_bin_read_byte(field82);
    if (file_bin_size(field82) == 60) {
        field84 = 48;
    } else {
        field84 = 60;
    }
    for (field29 = 1; field29 <= field84; field29 += 1) {
        global.field26[field29] = file_bin_read_byte(field82);
    }
}
file_bin_close(field82);

#define script30
var field82, field83, field87;
field82 = file_bin_open(working_directory + "/Data/DeathTime", 1);
field83 = global.field85;
file_bin_write_byte(field82, floor(field83 / 100000));
field83 -= floor(field83 / 100000) * 100000;
file_bin_write_byte(field82, floor(field83 / 10000));
field83 -= floor(field83 / 10000) * 10000;
file_bin_write_byte(field82, floor(field83 / 100));
field83 -= floor(field83 / 100) * 100;
file_bin_write_byte(field82, field83);
field87 = global.field25;
file_bin_write_byte(field82, floor(field87 / 1000000));
field87 -= floor(field87 / 1000000) * 1000000;
file_bin_write_byte(field82, floor(field87 / 10000));
field87 -= floor(field87 / 10000) * 10000;
file_bin_write_byte(field82, floor(field87 / 100));
field87 -= floor(field87 / 100) * 100;
file_bin_write_byte(field82, field87);
field87 = global.field86;
file_bin_write_byte(field82, floor(field87 / 1000000));
field87 -= floor(field87 / 1000000) * 1000000;
file_bin_write_byte(field82, floor(field87 / 10000));
field87 -= floor(field87 / 10000) * 10000;
file_bin_write_byte(field82, floor(field87 / 100));
field87 -= floor(field87 / 100) * 100;
file_bin_write_byte(field82, field87);
for (field29 = 1; field29 <= 60; field29 += 1) {
    file_bin_write_byte(field82, global.field26[field29]);
}
file_bin_close(field82);

saveData:

#define script32
var field82, field88, field89;
field82 = file_bin_open(working_directory + "/Data/saveData", 1);
field88 = global.field90;
file_bin_write_byte(field82, floor(field88 / 100000));
field88 -= floor(field88 / 100000) * 100000;
file_bin_write_byte(field82, floor(field88 / 10000));
field88 -= floor(field88 / 10000) * 10000;
file_bin_write_byte(field82, floor(field88 / 100));
field88 -= floor(field88 / 100) * 100;
file_bin_write_byte(field82, field88);
field89 = room;
field89 *= 152;
file_bin_write_byte(field82, floor(field89 / 10000));
field89 -= floor(field89 / 10000) * 10000;
file_bin_write_byte(field82, floor(field89 / 100));
field89 -= floor(field89 / 100) * 100;
file_bin_write_byte(field82, field89);
field89 = round(object7.x);
field89 *= 172;
file_bin_write_byte(field82, floor(field89 / 10000));
field89 -= floor(field89 / 10000) * 10000;
file_bin_write_byte(field82, floor(field89 / 100));
field89 -= floor(field89 / 100) * 100;
file_bin_write_byte(field82, field89);
field89 = round(object7.y);
if (room == 619) {
    field89 -= 1;
}
field89 *= 182;
file_bin_write_byte(field82, floor(field89 / 10000));
field89 -= floor(field89 / 10000) * 10000;
file_bin_write_byte(field82, floor(field89 / 100));
field89 -= floor(field89 / 100) * 100;
file_bin_write_byte(field82, field89);
file_bin_write_byte(field82, global.field91);
file_bin_write_byte(field82, global.field92);
file_bin_write_byte(field82, global.field93);
file_bin_write_byte(field82, global.field94);
file_bin_write_byte(field82, global.field95);
file_bin_write_byte(field82, global.field96);
file_bin_write_byte(field82, global.field97);
file_bin_write_byte(field82, global.field98);
file_bin_write_byte(field82, global.field99);
file_bin_write_byte(field82, global.field100);
file_bin_write_byte(field82, global.field101);
file_bin_write_byte(field82, global.field102);
file_bin_write_byte(field82, global.field103);
file_bin_write_byte(field82, global.field104);
file_bin_write_byte(field82, global.field105);
file_bin_write_byte(field82, global.field106);
file_bin_write_byte(field82, global.field107);
file_bin_write_byte(field82, global.field108);
file_bin_write_byte(field82, global.field109);
file_bin_write_byte(field82, global.field110);
file_bin_write_byte(field82, global.field111);
file_bin_write_byte(field82, global.field112);
file_bin_write_byte(field82, global.field113);
file_bin_write_byte(field82, global.field114);
file_bin_write_byte(field82, global.field115);
file_bin_write_byte(field82, global.field116);
file_bin_write_byte(field82, global.field117);
file_bin_write_byte(field82, global.field118);
file_bin_write_byte(field82, global.field119);
file_bin_write_byte(field82, global.field120);
file_bin_write_byte(field82, global.field121);
file_bin_write_byte(field82, global.field122);
file_bin_write_byte(field82, global.field123);
file_bin_write_byte(field82, global.field124);
file_bin_write_byte(field82, global.field125);
file_bin_write_byte(field82, global.field126);
file_bin_write_byte(field82, global.field127);
file_bin_write_byte(field82, global.field128);
file_bin_write_byte(field82, global.field129);
file_bin_write_byte(field82, global.field130);
file_bin_write_byte(field82, global.field131);
file_bin_write_byte(field82, global.field132);
file_bin_write_byte(field82, global.field133);
file_bin_write_byte(field82, global.field134);
file_bin_write_byte(field82, global.field135);
file_bin_write_byte(field82, global.field136);
file_bin_write_byte(field82, global.field137);
file_bin_write_byte(field82, global.field138);
file_bin_write_byte(field82, global.field139);
file_bin_close(field82);
for (field29 = 1; field29 <= 50; field29 += 1) {
    if (global.field30[field29] == 1) {
        global.field30[field29] = 2;
    }
}
script247();
script30();
if (global.field140 == 0) {
    global.field140 = 1;
}

#define script33
var field82, field88, field89, field141, field142;
field82 = file_bin_open(working_directory + "/Data/saveData", 0);
field88 = file_bin_read_byte(field82) * 100000;
field88 += file_bin_read_byte(field82) * 10000;
field88 += file_bin_read_byte(field82) * 100;
field88 += file_bin_read_byte(field82);
if (field88 != global.field90) {
    show_message("Wrong Savefile!");
    game_end();
    exit;
}
var field143;
if (!instance_exists(7)) {
    instance_create(0, 0, 7);
}
field143 += file_bin_read_byte(field82) * 10000;
field143 += file_bin_read_byte(field82) * 100;
field143 += file_bin_read_byte(field82);
field143 /= 152;
if (frac(field143) != 0) {
    show_message("Wrong Savefile!");
    game_end();
}
field141 += file_bin_read_byte(field82) * 10000;
field141 += file_bin_read_byte(field82) * 100;
field141 += file_bin_read_byte(field82);
field141 /= 172;
if (frac(field141) != 0) {
    show_message("Wrong Savefile!");
    game_end();
}
field142 += file_bin_read_byte(field82) * 10000;
field142 += file_bin_read_byte(field82) * 100;
field142 += file_bin_read_byte(field82);
field142 /= 182;
if (frac(field142) != 0) {
    show_message("Wrong Savefile!");
    game_end();
}
global.field91 = file_bin_read_byte(field82);
global.field92 = file_bin_read_byte(field82);
global.field93 = file_bin_read_byte(field82);
global.field94 = file_bin_read_byte(field82);
global.field95 = file_bin_read_byte(field82);
global.field96 = file_bin_read_byte(field82);
global.field97 = file_bin_read_byte(field82);
global.field98 = file_bin_read_byte(field82);
global.field99 = file_bin_read_byte(field82);
global.field100 = file_bin_read_byte(field82);
global.field101 = file_bin_read_byte(field82);
global.field102 = file_bin_read_byte(field82);
global.field103 = file_bin_read_byte(field82);
global.field104 = file_bin_read_byte(field82);
global.field105 = file_bin_read_byte(field82);
global.field106 = file_bin_read_byte(field82);
global.field107 = file_bin_read_byte(field82);
global.field108 = file_bin_read_byte(field82);
global.field109 = file_bin_read_byte(field82);
global.field110 = file_bin_read_byte(field82);
global.field111 = file_bin_read_byte(field82);
global.field112 = file_bin_read_byte(field82);
global.field113 = file_bin_read_byte(field82);
global.field114 = file_bin_read_byte(field82);
global.field115 = file_bin_read_byte(field82);
global.field116 = file_bin_read_byte(field82);
global.field117 = file_bin_read_byte(field82);
global.field118 = file_bin_read_byte(field82);
global.field119 = file_bin_read_byte(field82);
global.field120 = file_bin_read_byte(field82);
global.field121 = file_bin_read_byte(field82);
global.field122 = file_bin_read_byte(field82);
global.field123 = file_bin_read_byte(field82);
global.field124 = file_bin_read_byte(field82);
global.field125 = file_bin_read_byte(field82);
if (global.field125 == 0) {
    file_bin_close(field82);
    if (global.field26[3] == 1) {
        global.field126 = 1;
    }
    if (global.field26[7] == 1) {
        global.field127 = 1;
    }
    if (global.field26[11] == 1) {
        global.field128 = 1;
    }
    if (global.field26[15] == 1) {
        global.field129 = 1;
    }
} else {
    global.field126 = file_bin_read_byte(field82);
    global.field127 = file_bin_read_byte(field82);
    global.field128 = file_bin_read_byte(field82);
    global.field129 = file_bin_read_byte(field82);
    global.field130 = file_bin_read_byte(field82);
    global.field131 = file_bin_read_byte(field82);
    global.field132 = file_bin_read_byte(field82);
    global.field133 = file_bin_read_byte(field82);
    global.field134 = file_bin_read_byte(field82);
    global.field135 = file_bin_read_byte(field82);
    global.field136 = file_bin_read_byte(field82);
    global.field137 = file_bin_read_byte(field82);
    global.field138 = file_bin_read_byte(field82);
    global.field139 = file_bin_read_byte(field82);
    file_bin_close(field82);
    script248();
}
if (room_get_name(field143) == "<undefined>") {
    if (global.field111 < 1) {
        show_message("You must clear 1st boss!");
        game_end();
    } else {
        room_goto(683);
        object7.x = 16;
        object7.y = 336;
    }
} else {
    room_goto(field143);
    object7.x = field141;
    object7.y = field142;
    if (global.field125 == 0) {
        global.field125 = 1;
        script32();
    }
}

saveData2

#define script247
var field82, field88, field29, field686;
field82 = file_bin_open(working_directory + "/Data/saveData2", 1);
field88 = global.field687;
file_bin_write_byte(field82, floor(field88 / 100000));
field88 -= floor(field88 / 100000) * 100000;
file_bin_write_byte(field82, floor(field88 / 10000));
field88 -= floor(field88 / 10000) * 10000;
file_bin_write_byte(field82, floor(field88 / 100));
field88 -= floor(field88 / 100) * 100;
file_bin_write_byte(field82, field88);
for (field29 = 1; field29 <= 50; field29 += 1) {
    file_bin_write_byte(field82, global.field30[field29]);
}
file_bin_close(field82);
for (field29 = 1; field29 <= 50; field29 += 1) {
    if (global.field30[field29] == 2) {
        field686 += 1;
    }
}
if (field686 == 50) {
    if (global.field26[57] == 0) {
        global.field26[57] = 1;
        field27 = instance_create(x, y, 1444);
        field27.field28 = 57;
        script30();
    }
}

#define script248
var field82, field29, field88, field688;
if (file_exists(working_directory + "/Data/saveData2") == 1) {
    field82 = file_bin_open(working_directory + "/Data/saveData2", 0);
    field88 = file_bin_read_byte(field82) * 100000;
    field88 += file_bin_read_byte(field82) * 10000;
    field88 += file_bin_read_byte(field82) * 100;
    field88 += file_bin_read_byte(field82);
    if (field88 != global.field687) {
        show_message("Wrong Savefile!");
        game_end();
        exit;
    }
    if (file_bin_size(field82) == 44) {
        field688 = 40;
    } else {
        field688 = 50;
    }
    for (field29 = 1; field29 <= field688; field29 += 1) {
        global.field30[field29] = file_bin_read_byte(field82);
    }
    for (field29 = 1; field29 <= field688; field29 += 1) {
        if (global.field30[field29] == 2) {
            field686 += 1;
        }
    }
    file_bin_close(field82);
    if (field688 == 40) {
        global.field130 = 0;
        global.field131 = 0;
        global.field132 = 0;
        global.field133 = 0;
        global.field124 = 0;
        global.field135 = 0;
        global.field136 = 0;
        global.field26[60] = 0;
        global.field26[59] = 0;
        global.field26[58] = 0;
        global.field26[57] = 0;
        global.field26[56] = 0;
        global.field26[55] = 0;
        global.field26[54] = 0;
        global.field26[53] = 0;
        script30();
    }
}

What the hell?

tl;dr: KTK3 does save file verification through checking the first $n$ bytes of savefile as some chosen decimal digits of the random number generated on first launch. The following are standard Yuutu-engine style savefile.

fundimentally broken lmao

PoC

bruh too lazy, do it urself

mochaaP/ktk3_savefile.md

KTK3 savefile analysis

Fields

Validation

What the hell?

PoC