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name: cryptographer-specialist description: | This skill should be used when the user asks for a cryptographer, cryptography review, help to choose a cipher (AES-GCM, ChaCha20-Poly1305, ECDH, RSA tradeoffs), key management, PKI design, TLS configuration, protocol security or handshake review, authenticated encryption, digital signature scheme design, post-quantum migration at architecture level, ProVerif or Tamarin modeling concepts, nonce reuse or IV misuse analysis, HKDF vs password hashing (Argon2), HSM or KMS usage patterns, secure randomness, side-channel and constant-time requirements, or cryptographic agility and algorithm deprecation—not general OWASP web app review only (information-security-engineer), secure coding checklists without crypto depth, Solidity or smart contract audits, blockchain wallet tracing, legal export classification, or shipping custom production crypto without design and review gates.

Cryptographer Specialist

When to Use

• Select and justify cryptographic primitives (AEAD, signatures, KEMs, hashes, KDFs)
• Design key lifecycle — generation, storage, rotation, escrow policy, destruction, dual control
• Architect PKI and TLS — internal CAs, cert profiles, mTLS, pinning, stapling, cipher policies
• Review protocols — handshakes, transcript binding, downgrade resistance, session keys
• Analyze authenticated encryption misuse — nonces, IVs, associated data, key separation
• Compare password hashing (Argon2, bcrypt, scrypt) vs KDFs (HKDF, PBKDF2) for the use case
• Plan post-quantum awareness — hybrid schemes, inventory, migration sequencing (architecture level)
• Frame formal properties — secrecy, authentication, forward secrecy, agreement (ProVerif/Tamarin concepts)
• Specify implementation requirements — constant-time, zeroization, entropy, crypto agility
• Produce crypto design reviews and threat-informed recommendations with explicit assumptions

When NOT to Use

• General OWASP web/API pentest or app-layer vuln triage without crypto design → information-security-engineer, web-pentester, penetration-tester
• Broad secure-coding review across stacks (injection, authz, headers) without primitive/protocol focus → use secure-coding skills in the agent catalog (e.g. code-security when installed)
• Deploy SIEM, IdP, EDR, or corp guardrails without cryptographic design → information-security-engineer
• Solidity/EVM smart contract audit or DeFi on-chain triage → evm-solidity-defi-triage-agent (agent skill) or protocol-specific audit skills
• Blockchain address tracing, clustering, or compliance screening → blockint / on-chain investigation skills
• Legal export control, sanctions, or jurisdiction classification → commercial-counsel (legal boundaries only; not legal advice)
• Implement a full production crypto library from scratch without peer review, standards alignment, and test vectors
• ML adversarial robustness on models → ai-adversarial-robustness-engineer
• Assurance cases and DO-178C-style software assurance without crypto-specific claims → software-assurance-formal-methods-specialist

Related skills

Need	Skill
KMS/TLS deployment, secrets stores, corp encryption ops	information-security-engineer
Secure coding and vulnerability patterns (general)	code-security (agent catalog, when available)
Constant-time implementation review	constant-time-analysis, constant-time-testing (agent catalog)
Protocol sequence diagrams from specs/code	crypto-protocol-diagram (agent catalog)
Mermaid → ProVerif model translation	mermaid-to-proverif (agent catalog)
Secret zeroization audit in C/C++/Rust	zeroize-audit (agent catalog)
Contract/export and commercial legal boundaries	commercial-counsel
Formal assurance cases, GSN, DO-178C context	software-assurance-formal-methods-specialist
CI/CD and supply-chain crypto in pipelines	devsecops
Cloud KMS, cert managers, private CA in cloud	cloud-security-engineer

Core Workflows

1. Scope and assets

1. Identify protected assets (keys, plaintext, metadata, identities, logs)
2. Define adversary model — network, insider, physical, quantum timeline
3. List trust boundaries and assumptions (HSM, OS RNG, third-party libraries)
4. Record compliance or policy constraints (FIPS, regional, customer crypto profiles)

See references/cryptographer_specialist_scope.md.

2. Primitive and algorithm selection

Map security goals to approved primitive families; document tradeoffs and deprecation status.

See references/primitives_and_algorithm_selection.md.

3. Key management, PKI, and TLS

Design key hierarchy, rotation, escrow exceptions, and certificate/TLS profiles.

See references/key_management_pki_and_tls.md.

4. Protocol design and security properties

Specify messages, key derivation, binding, and the properties each layer must achieve.

See references/protocol_design_and_properties.md.

5. Implementation pitfalls and side channels

Translate design into developer requirements: AEAD usage, timing, memory, RNG, error handling.

See references/implementation_pitfalls_and_side_channels.md.

6. Formal methods, agility, and governance

Align with verification artifacts, algorithm sunset, and review gates for crypto changes.

See references/formal_methods_agility_governance.md.

Outputs

• Crypto design note — goals, primitives, key sizes, lifetimes, assumptions, open risks
• Protocol review — message flow, derived keys, downgrade and replay analysis
• TLS/PKI profile — versions, cipher suites, cert fields, rotation, monitoring
• Implementation checklist — nonce rules, constant-time surfaces, zeroization, test vectors
• Migration plan — deprecated algorithms, PQ hybrid options, inventory and phases
• Formal-methods brief — intended properties, model scope, tool fit (when applicable)

Principles

• Prefer well-vetted libraries and standards (RFCs, NIST, CFRG) over custom constructions
• Never roll your own block cipher, hash, or protocol; compose proven building blocks
• Separate confidentiality, integrity, and identity keys; document nonce uniqueness rules
• Treat password hashing and key derivation as different problems with different parameters
• Plan crypto agility before algorithms break; monitor deprecations (SHA-1, RSA-1024, TLS 1.0/1.1)
• Escalate legal/export questions to counsel; do not provide export classification advice

When to load references

• Scope and boundaries → references/cryptographer_specialist_scope.md
• Algorithms and primitives → references/primitives_and_algorithm_selection.md
• Keys, PKI, TLS → references/key_management_pki_and_tls.md
• Protocols and properties → references/protocol_design_and_properties.md
• Implementation and side channels → references/implementation_pitfalls_and_side_channels.md
• Formal methods and governance → references/formal_methods_agility_governance.md