# Crypto Ctf > Lab/CTF: crypto challenges; ciphertexts, keys, signatures, oracles, transcripts, PRNG, RSA/ECC/lattice/math protocol code. - Skill: `aeondave/crypto-ctf` (Agent Skill, multi-file: 14 files) - Install (CLI): `npx skillmds@latest add aeondave/crypto-ctf` - Raw SKILL.md: https://api.skillmd.com/api/skills/aeondave/crypto-ctf/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - License: MIT - Author: AeonDave (https://skillmd.com/u/aeondave) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/aeondave/crypto-ctf --- # Crypto CTF Goal: solve cryptography challenge solving tasks with professional offensive methodology, preserved imported technique coverage, and reproducible evidence. ## When this skill applies - ciphertexts, keys, signatures, oracles, transcripts, proofs, PRNG outputs, or mathematical protocol code - RSA, ECC, DH, DSA/ECDSA, lattice/LWE, PRNG, symmetric-mode, stream-cipher, ZKP, secret-sharing, or exotic algebraic weaknesses ## Operating model 1. Classify the dominant artifact, primitive, or objective. 2. Load the closest `offensive-techniques` methodology before selecting tools. 3. Load references only for deep technique details. 4. Choose the smallest tool chain that can produce a validation signal. 5. Record the exact proof path and stop once the objective is reproducible. ## Technique integration Primary methodology to load: - `crypto-technique` - `cracking-technique` Use these as decision engines. This skill adds challenge-oriented triage, time-boxing, and preserved specialized patterns from the imported corpus. ## Tool routing Prefer these tool families when the corresponding signal appears: - `rsactftool` - `sagemath` - `cyberchef` - `hashcat` - `john` - `coding/python-patterns` Tool syntax belongs in the tool skills. This skill decides when a tool family fits and what output should validate progress. ## Category-specific quick pivots - Extract parameters before choosing attacks: modulus, exponent, curve order, nonce, IV, oracle response, random source, and serialization. - Rank attacks by structural evidence: factorability, smoothness, nonce reuse, small roots, linear recurrence, or mode misuse. - Validate recovered material by re-encryption, signature verification, oracle replay, or known plaintext. ## Targeted hint research gate If local triage has already classified the primitive, ranked attacks, and still hit a specific wall, load `knowledge/known-problem-hint-research`. Use it only as a post-triage spike to find a paper, blog, article, public analysis, source discussion, or implementation note that maps to the exact problem fingerprint. Do not use it as broad search or before the local pivot ledger has evidence. ## Quality gates - No claim without a validation signal: recovered secret, replayed exploit, decoded artifact, reproduced model behavior, or corroborated evidence. - Do not brute force before representation, constraints, and success oracle are known. - Keep a pivot ledger: hypothesis, evidence, result, next shortest path. - Preserve coverage by keeping every operational topic reachable from the Resources routing below. - Keep challenge/platform/competition names out of notes and generated reports. ## Resources ### Modern Cipher Attacks - [references/modern-cipher-modes-and-forgery.md](references/modern-cipher-modes-and-forgery.md) — AES/CFB/CBC/CTR/GCM/OFB mode failures, padding and decode oracles, bit-flip/cut-and-paste forgeries, cookie/session tampering, and practical ciphertext manipulation workflows. - [references/modern-hash-mac-and-collision-attacks.md](references/modern-hash-mac-and-collision-attacks.md) — Hash/MAC weaknesses: length extension, CRC misuse, chosen-prefix and multi-collision workflows, linear-MAC breaks, and aggregate-hash forgery patterns. - [references/modern-oracles-protocols-and-custom-crypto.md](references/modern-oracles-protocols-and-custom-crypto.md) — Protocol and design failures: Bleichenbacher/Rabin/Blum-Goldwasser oracles, SRP and KDF flaws, reduced-round/custom constructions, and algebraic attack pivots. ### RSA Attacks - [references/rsa-attacks.md](references/rsa-attacks.md) — Small exponent recovery, common modulus attacks, Wiener's attack, Pollard p-1 factorization, Hastad broadcast, Fermat factorization, multi-prime RSA, restricted-digit primes, Coppersmith attacks, Manger's padding oracle, specialized RSA (p=q bypass, gcd(e,phi)>1, phi-multiple factoring, CRT faults, homomorphic bypass, batch GCD, partial key recovery), signature forgery (homomorphic, Bleichenbacher, low-exponent), ROCA attack (CVE-2017-15361), timing attacks, dependent-prime RSA, three-key GCD. ### Exotic Cryptography - [references/exotic-crypto.md](references/exotic-crypto.md) — Braid group DH (Alexander polynomial multiplicativity), monotone function inversion, tropical semiring residuation, Paillier homomorphic encryption, Hamming codes, ElGamal variants, format-preserving encryption Feistel, icosahedral symmetry group cipher, Goldwasser-Micali ciphertext replication, BB-84 quantum key distribution MITM. ### PRNG & Key Recovery - [references/prng.md](references/prng.md) — Mersenne Twister state recovery (untemper, symbolic solving), MT from random.random() floats via GF(2) matrix (not_random library), time-based seed attacks, C srand/rand via ctypes, layered encryption recovery, LCG parameter recovery, ChaCha20 key recovery, GF(2) matrix PRNG seed recovery, middle-square PRNG brute-force, deterministic RNG from flag bytes (hill climbing), byte-by-byte oracle, RSA key reuse, logistic map/chaotic PRNG seed recovery, V8 XorShift128+ state recovery (Math.random prediction), and CTF-era advanced techniques (MT constraint propagation, Z3 timing oracle, cellular automaton LFSR, Java LCG MITM), EC-LCG state recovery from truncated EC coordinates. ### Elliptic Curve Attacks - [references/ecc-attacks.md](references/ecc-attacks.md) — Small subgroup attacks, invalid curve attacks, Smart's attack, ECDSA nonce reuse, curve order factorization, twist attacks, anomalous curves, special-form curve weaknesses, BLS aggregate signature rogue-key attacks, proof-of-possession bypass. ### Advanced Mathematics - [references/advanced-math.md](references/advanced-math.md) — Isogenies and CSIDH, Pohlig-Hellman algorithm, LLL lattice reduction, Coppersmith small-roots method, Clock group DLP, Babai nearest-plane algorithm, CVP/SVP solvers, GF(2) linear algebra, generalized birthday attacks, sparse polynomial systems. ### Lattice & LWE - [references/lattice-and-lwe.md](references/lattice-and-lwe.md) — Lattice problems (SVP, CVP, HNP), LWE attacks (Gaussian elimination, BKZ reduction), hidden number problem, ECDSA partial-nonce recovery via lattice, LWE parameter tweaking, NTRU attacks. ### Classic Ciphers - [references/classic-ciphers.md](references/classic-ciphers.md) — Vigenere cipher frequency analysis, Atbash simple substitution, Polybius square attacks, substitution cipher key recovery, XOR-based cipher analysis, pattern matching and constraint solving. ### Stream Ciphers - [references/stream-ciphers.md](references/stream-ciphers.md) — LFSR feedback polynomial recovery, RC4 state recovery and keystream prediction, XOR-based stream cipher weaknesses, mode misuse (reusing nonces/IVs), correlated keystream analysis. ### Historical Ciphers - [references/historical.md](references/historical.md) — Lorenz SZ40/42 rotor machine analysis, book cipher key recovery, pre-modern cryptanalysis techniques, mechanical cipher exploitation. ### ZKP & Advanced Techniques - [references/zkp-and-advanced.md](references/zkp-and-advanced.md) — Zero-knowledge proof attacks, interactive proof verification bypass, Z3 SMT solver application, garbled circuits (generator/evaluator attacks), Shamir secret sharing, race conditions in crypto protocols, Fiat-Shamir heuristic vulnerabilities.