Crypto Analysis Skill for Claude

Cryptographic Analysis

When to Activate

• Auditing TLS/SSL/SSH configurations and X.509 PKI (cipher suites, downgrade, protocol flaws)
• Reviewing crypto implementations in source code or captured traffic
• Attacking weak RSA/ECC keys (CTF and real-world weak-key hygiene)
• Recovering ECDSA/DSA private keys from reused or biased nonces (lattice/HNP)
• Exploiting symmetric/AEAD misuse: padding oracles, GCM nonce reuse, key-commitment
• Forging JWT/JOSE tokens (algorithm confusion, none, jwk/jku/kid injection)
• Cracking password hashes and grading KDF strength
• Assessing post-quantum readiness ("harvest now, decrypt later" exposure)

Technique Map

| Technique | ATT&CK | CWE | Reference | Script |

|-----------|--------|-----|-----------|--------|

| TLS cipher/protocol downgrade audit | T1600.001 | CWE-326 | references/tls-pki-audit.md | scripts/tls_audit.py |

| Terrapin SSH prefix truncation (CVE-2023-48795) | T1557 | CWE-222 | references/tls-pki-audit.md | scripts/tls_audit.py |

| Marvin/Bleichenbacher RSA timing oracle | T1600 | CWE-208 | references/tls-pki-audit.md | scripts/tls_audit.py |

| X.509 / CT-log shadow-asset discovery | T1589 | CWE-295 | references/tls-pki-audit.md | scripts/tls_audit.py |

| RSA weak-key factoring (Fermat/Wiener/common-modulus) | T1600 | CWE-326 | references/rsa-attacks.md | scripts/rsa_attack.py |

| Coppersmith partial-key & ROCA (CVE-2017-15361) | T1600 | CWE-310 | references/rsa-attacks.md | scripts/rsa_attack.py |

| Hastad broadcast / batch-GCD | T1600 | CWE-326 | references/rsa-attacks.md | scripts/rsa_attack.py |

| ECDSA nonce reuse key recovery | T1552.004 | CWE-323 | references/ecc-nonce-attacks.md | scripts/ecdsa_lattice.py |

| Biased-nonce lattice/HNP (Minerva, PuTTY CVE-2024-31497) | T1552.004 | CWE-1241 | references/ecc-nonce-attacks.md | scripts/ecdsa_lattice.py |

| Psychic signature (0,0) (CVE-2022-21449) | T1606.001 | CWE-347 | references/ecc-nonce-attacks.md | scripts/ecdsa_lattice.py |

| CBC padding oracle (byte-by-byte decrypt) | T1040 | CWE-209 | references/symmetric-aead.md | scripts/padding_oracle.py |

| AES-GCM nonce reuse "forbidden attack" | T1040 | CWE-323 | references/symmetric-aead.md | scripts/gcm_nonce_reuse.py |

| AEAD key-commitment / invisible salamanders / partitioning oracle | T1606 | CWE-347 | references/symmetric-aead.md | scripts/gcm_nonce_reuse.py |

| JWT algorithm confusion RS256→HS256 (CVE-2024-54150) | T1606.001 | CWE-347 | references/jwt-jose.md | scripts/jwt_forge.py |

| JWT alg=none / jwk / jku / kid injection | T1606.001 | CWE-347 | references/jwt-jose.md | scripts/jwt_forge.py |

| Hash identification & GPU cracking | T1110.002 | CWE-916 | references/hash-pq.md | scripts/hash_triage.py |

| Weak KDF / fast-hash password storage | T1110.002 | CWE-916 | references/hash-pq.md | scripts/hash_triage.py |

| Post-quantum / HNDL exposure review | T1600 | CWE-327 | references/hash-pq.md | scripts/tls_audit.py |

Quick Start

# 0. TLS/PKI posture in one shot (downgrade, ROBOT, SWEET32, Terrapin, cert/CT)
python3 scripts/tls_audit.py target.com:443 --ssh target.com:22 --ct --json out.json
testssl.sh --full --robot --sweet32 https://target.com   # cross-check with the canonical tool

# 1. RSA weak-key triage on a captured public key
python3 scripts/rsa_attack.py --pubkey server.pem --ct ciphertext.b64 --auto
#   tries Fermat (p~=q), Wiener (small d), batch-GCD/common-modulus, ROCA fingerprint

# 2. ECDSA key recovery from a signature corpus (reuse or bias)
python3 scripts/ecdsa_lattice.py recover sigs.json --curve secp256r1 --known-msb 4
#   reuse: needs 2 sigs w/ same r; bias: ~256-1200 sigs depending on leak

# 3. Symmetric/AEAD misuse
python3 scripts/padding_oracle.py --url https://t/dec --ct $CT --block 16   # CBC oracle
python3 scripts/gcm_nonce_reuse.py forbidden ct1.bin ct2.bin --nonce $N     # recover H + forge

# 4. JWT forgery chain
python3 scripts/jwt_forge.py confusion --pubkey jwt_pub.pem --claims '{"role":"admin"}'
python3 scripts/jwt_forge.py none      --claims '{"sub":"admin"}'

# 5. Hash triage + crack plan
python3 scripts/hash_triage.py hashes.txt            # identify + emit hashcat -m / john format
hashcat -m 22000 capture.hc22000 wl.txt -r rules/best64.rule

OPSEC & Detection (summary)

| Technique | Telemetry / IOC | Detection (Sigma/EDR) | OPSEC note |

|-----------|-----------------|-----------------------|------------|

| TLS scanning / testssl | Burst of handshakes, many cipher renegotiations, malformed ClientHellos | NIDS: high TLS alert rate from one src; Zeek ssl.log anomalous cipher offers | Rate-limit, spread across source IPs; passive cert/CT recon leaves no target-side trace |

| Marvin/ROBOT oracle probing | ~10^4–10^6 RSA decrypts, repeated malformed pre-master/CMS | WAF/IDS: spike of TLS decrypt errors, identical-size payloads | Extremely loud; only against authorized hosts; use minimal query budgets |

| Terrapin MitM | Injected SSH_MSG_IGNORE, sequence-number gap at NEWKEYS | SSH server logs kex mismatch; netflow showing on-path device | Requires active MitM; detectable by strict-kex peers; abort if kex-strict present |

| ECDSA nonce harvesting | Bulk signature collection (Git, TLS, SSH, blockchain) | Mostly offline — no target telemetry once sigs captured | Collection is passive; recovery is offline; rotate-key advice in report |

| CBC padding oracle | Thousands of decrypt requests, alternating valid/invalid padding | Web logs: ~256×blocks requests to one endpoint; Sigma on 4xx burst | Very noisy (256×blocks×msgs); throttle, randomize timing |

| GCM nonce reuse / partitioning | Repeated (nonce,key) pairs; multi-key ciphertext blobs | App crypto audit; flag reused IVs in logs | Forbidden-attack math is offline once two ciphertexts captured |

| JWT forgery | Anomalous alg, external jku/x5u fetch, all-zero ES signature | Sigma: JWT with alg:none/HS after RS expected; egress to attacker JWKS URL | Each forged token is a single request; minimal noise |

| Hash cracking | None on target (offline) | N/A unless online spray (then T1110) | Offline; protect loot at rest; never spray live without scope |

Deep Dives

• references/tls-pki-audit.md — TLS/SSL/SSH posture: cipher/protocol downgrade, Terrapin (CVE-2023-48795), Marvin/Bleichenbacher (CVE-2022-4304, CVE-2024-2236), SWEET32/DROWN/Logjam/POODLE, X.509 and Certificate-Transparency analysis.
• references/rsa-attacks.md — Weak-key factoring: Fermat, Wiener, common modulus, Hastad broadcast, Coppersmith partial-key, batch-GCD, ROCA (CVE-2017-15361); RsaCtfTool / cado-nfs / SageMath workflow.
• references/ecc-nonce-attacks.md — ECDSA/DSA nonce reuse, biased-nonce lattice/HNP recovery (Minerva, PuTTY CVE-2024-31497), invalid-curve attacks, psychic signatures (CVE-2022-21449).
• references/symmetric-aead.md — Block-cipher mode misuse: ECB detection, CBC padding oracle, CTR/GCM nonce reuse (forbidden attack), AEAD key-commitment / invisible salamanders / partitioning oracles.
• references/jwt-jose.md — JWT/JOSE token forgery: algorithm confusion (CVE-2024-54150), alg=none, jwk/jku/x5u/kid injection, weak-secret cracking, library-level CVE landscape.
• references/hash-pq.md — Hash identification, modern GPU cracking economics (RTX 40/50-series), KDF strength grading, and post-quantum migration / "harvest now, decrypt later" assessment (ML-KEM/ML-DSA, hybrid TLS, crypto-agility).