asepharyana
f9ae3d8808
- examples/bodu: full Boneh-Durfee lattice attack (fpylll LLL + sympy gcd extraction), verified on a toy RSA; live instance needs larger m (k>n^0.292) - examples/crypto_baby: hidden-base knapsack 0/1-digit recovery reference - examples/README.md: split verified solves (5) from reference implementations
45 lines
2.4 KiB
Markdown
45 lines
2.4 KiB
Markdown
# Examples — real CTF challenges solved with this toolkit
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Every VERIFIED example is reproducible offline (no live server, no sage) and
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uses `lib/crypto_utils.py` / `lib/net.py` where applicable. Solved by distilling
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patterns from the public `p4-team/ctf` archive.
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## Solved (flag recovered)
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| Challenge | Event | Category | Vuln | Flag |
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|-----------|-------|----------|------|------|
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| `ps_and_qs` | SECCON 2017 Quals | Crypto | Two RSA keys share a prime (`gcd(n1,n2)=p`) | `SECCON{1234567890ABCDEF}` |
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| `lost_modulus` | HITCON 2019 Quals | Crypto | RSA leaks `e,d,iqmp,ipmq` but not `n` — recover `n` | `hitcon{1t_is_50_easy_t0_find_th3_modulus_back@@!!@!@!@@!}` |
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| `a2s` | Pwn2Win 2021 | Crypto | 2-round reduced AES — differential attack recovers key | `CTF-BR{bu7_1f_7h0u6h7_c0rrup75_l4n6u463,_l4n6u463_c4n_4l50_c0rrup7_7h0u6h7}` |
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| `russian_threesome` | Hack.lu 2020 | RE/Misc | Inverse-permutation fixed-point on a drum dump (CP1251) | `Кто хочет много знать, тому мало спать.` |
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| `mask` | TokyoWesterns 2020 | Misc | Host bits of `IP/mask` list → base64 → flag | `TWCTF{Are-you-using-a-mask?}` |
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## Reference implementations (attack coded, solver recovery pending)
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These contain correct, working implementations of the hard attack but the
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final root/key recovery for the specific live instance needs more tuning (or
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sage-grade `small_roots`). Kept as study references, **not** counted as solved.
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| Challenge | Event | Category | Implemented attack | Blocker |
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|-----------|-------|----------|--------------------|---------|
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| `bodu` | ASIS Finals 2015 | Crypto (HARD) | Full Boneh-Durfee lattice (LLL via fpylll) + sympy resultant/gcd extraction — **verified on a toy RSA** | Live instance has `k=e·d/φ ≈ n^0.325 > 0.292` BD limit; needs larger `m` / `+1` refinement |
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| `crypto_baby` | ASIS Finals 2018 | Crypto (HARD) | Hidden-base knapsack: base-`exp` 0/1-digit recovery | Live `exp`/`S`/`key` structure resists direct base-2 decode |
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## Run them
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```bash
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cd /home/code/ctfkit
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# crypto — self contained
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python3 examples/ps_and_qs.py
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python3 examples/lost_modulus/solve.py
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# a2s — runs the differential attack then extracts the flag
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cd examples/a2s && python3 solve.py && cd ../..
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# russian_threesome — permutation fixed point
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python3 examples/russian_threesome/solve.py
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# mask — IP/mask host bits -> base64
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python3 examples/mask/solve.py
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```
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