asepharyana
0de2458955
- Deleted all 14 dummy docs from DB + filesystem - Created 14 Gemastik warmup writeups + index via create_document API (DB-first) - ch1-ch12: encoding/stego/web/pwn basics - ch13: RSA small factors - ch14: RSA special integers via paper-search (GCD with paper appendix primes) - All 15 docs indexed and live at wiki.asepharyana.my.id
41 lines
1.0 KiB
Markdown
41 lines
1.0 KiB
Markdown
---
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title: "Layers — Hex to Base64 Chain"
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type: "writeup"
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section: "writeups"
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status: "published"
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author: "asep"
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tags: ["gemastik", "ctf", "warmup", "crypto"]
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path: "writeups/gemastik-2026-warmup/ch12-layers.md"
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created_at: "2026-08-21T07:25:48.559Z"
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updated_at: "2026-08-21T07:25:48.559Z"
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event: "GEMASTIK 2026 Warmup"
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challenge: "Layers — Hex to Base64 Chain"
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category: "crypto"
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points: 500
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difficulty: "easy"
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flag: "GEMASTIK19{h3x_lQlu_b4s3_ch41n}"
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---
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# Layers (500 pts) — Encoding chain
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**File:** `chall.txt` → `5230564e51564e55535573784f58746f4d33686662464673645639694e484d7a58324e6f4e44467566513d3d`
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Dua lapis encoding berturut-turut: **Hex → bytes → Base64 → flag**:
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```python
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import base64
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s = "5230564e51564e55535573784f58746f4d33686662464673645639694e484d7a58324e6f4e44467566513d3d"
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# Layer 1: hex decode
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b = bytes.fromhex(s)
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# b = b'R0VNQVNUSUsxOXtoM3hfbFFsdV9iNHMzX2NoNDFufQ=='
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# Layer 2: base64 decode
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flag = base64.b64decode(b).decode()
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print(flag)
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# GEMASTIK19{h3x_lQlu_b4s3_ch41n}
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```
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## Flag
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`GEMASTIK19{h3x_lQlu_b4s3_ch41n}` |