asepharyana
7a6e717c28
- Deleted all previous dummy docs (defcon-quals-2024, infra/cloudflare-525, debugging/websocket-timeout, template, docs/*, notes/*, research/*) - Added 14 Gemastik warmup writeups covering encoding, stego, web, pwn, crypto - ch13: RSA small factors; ch14: RSA special integers via paper-search (GCD with paper appendix primes) - All flags recovered and documented with solution methods
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1.0 KiB
title, event, challenge, category, points, difficulty, flag
| title | event | challenge | category | points | difficulty | flag |
|---|---|---|---|---|---|---|
| Sixty Four — Double Base64 | GEMASTIK 2026 Warmup | Sixty Four | crypto | 500 | easy | GEMASTIK19{b4s3_s1xty_f0ur_warm1ng_up} |
Sixty Four (500 pts) — Encoding
File: chall.txt → UjBWTlFWTlVTVXN4T1h0aU5ITXpYM014ZUhSNVgyWXdkWEpmZDJGeWJURnVaMTkxY0gwPQ==
Teks di-encode Base64 dua kali (hint: "sixty four" = base64). Decode berlapis:
$ echo "UjBWTlFWTlVTVXN4T1h0aU5ITXpYM014ZUhSNVgyWXdkWEpmZDJGeWJURnVaMTkxY0gwPQ==" | base64 -d
R0VNQVNUSUsxOXtiNHMzX3MxeHR5X2YwdXJfd2FybTFuZ191cH0=
$ echo "R0VNQVNUSUsxOXtiNHMzX3MxeHR5X2YwdXJfd2FybTFuZ191cH0=" | base64 -d
GEMASTIK19{b4s3_s1xty_f0ur_warm1ng_up}
Solusi Python
import base64
with open("chall.txt") as f:
s = f.read().strip()
# First base64 decode
decoded1 = base64.b64decode(s)
# Second base64 decode
flag = base64.b64decode(decoded1).decode()
print(f"Flag: {flag}")
# Output: GEMASTIK19{b4s3_s1xty_f0ur_warm1ng_up}
Flag
GEMASTIK19{b4s3_s1xty_f0ur_warm1ng_up}