SCSC2026 Quals - Hitungan MTK - General Skills Writeup

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1 minute

SCSC2026 Quals - Hitungan MTK - General Skills Writeup

2026-02-17

Writeup

CTF

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Security

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General Skills

Category: General Skills

Server: nc 43.128.69.211 10001

Flag: scsc26{p1nt3r_mtk_g4j4min_j4g0_scr1pt1ng_n_s0ck3t_pr0gr4mm1n6}

Challenge Description#

Connect to the server and solve 30 math problems within 1 second each.

Analysis#

Upon connecting, the server presents arithmetic problems that must be solved quickly. Manual solving is impossible due to the strict 1-second time limit per question.

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$ nc 43.128.69.211 10001
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Rockwell ada challenge berhitung UwU
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Ada 30 soal hitungan, cuma boleh jawab 1x dalam waktu 1 detik!
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====Rockwell====
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52+55 =

Key observations:

Multiplication uses x instead of *
Division uses : instead of /
Format is simple: <expr> = (no question mark, no problem number)
Must respond within 1 second or the question is skipped

Solution#

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# !/usr/bin/env python3
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from pwn import *
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import re
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def main():
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    p = remote('43.128.69.211', 10001)
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    # Wait for banner (ends with "====Rockwell====")
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    p.recvuntil(b'====Rockwell====', timeout=5)
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    for i in range(30):
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        # Receive until " = " which marks end of expression
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        line = p.recvuntil(b' = ', timeout=1).decode()
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        # Parse expression: replace x->*, :->/, strip " = "
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        expr = line.replace('x', '*').replace(':', '/').replace(' = ', '').strip()
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        # Solve
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        result = eval(expr)
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        # Key insight: division needs 3 decimal places
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        if '/' in expr:
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            result = round(result, 3)
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        else:
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            result = int(result)
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        print(f"[{i+1}] {expr} = {result}")
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        p.sendline(str(result).encode())
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    # Receive flag
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    print(p.recvall(timeout=3).decode())
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if __name__ == '__main__':
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    main()

Key Insight#

Two critical discoveries:

Operators are different: x for multiplication, : for division (Indonesian convention)
Division results must be rounded to 3 decimal places using round(result, 3)