Crypto data protection

Crypto data protection (crypto.in-transit / crypto.at-rest) — authoring-time guidance

Scope: this skill helps you implement the encryption controls in code. It does not certify compliance. It makes the code satisfy the control and makes that statically detectable (these are code properties, not runtime events — there is no marker to emit).

Framework-neutral by design. The control keys crypto.in-transit / crypto.at-rest map to SOC 2 (CC6.7 / CC6.1), ISO 27001 (A.8.24), PCI-DSS v4 (Req 4.2 / 3.5), and HIPAA (164.312(e)(1) / 164.312(a)(2)(iv)) via the crosswalk.

When this applies

• In transit: any outbound request, network client, webhook, or service-to-service call; any TLS/SSL setup.
• At rest: schema or writes for sensitive data (PII, financial, health, credentials, tokens); file/object/blob storage; backups; caches that hold the above.

Ordinary in-process data with no network or persistence boundary does not need this skill.

1. Encrypt in transit — crypto.in-transit

• Always https:// / wss:// for anything leaving the process. Never http:// to a remote host (localhost during dev is fine).
• Never disable certificate verification. No verify=False (Python requests), no rejectUnauthorized: false (Node), no NODE_TLS_REJECT_UNAUTHORIZED=0, no _create_unverified_context. If a cert is failing, fix the trust store — don't turn off TLS.
• Prefer TLS 1.2+; let the platform negotiate rather than pinning weak ciphers.

# ✅ encrypted transport, verification on (the default)
requests.post("https://api.payments.example.com/charge", json=payload, timeout=10)

2. Encrypt at rest — crypto.at-rest

• Encrypt sensitive fields/blobs with a vetted library (Fernet, AES-GCM, libsodium/NaCl) or the datastore's native encryption (column encryption, KMS-backed envelope encryption).
• Keys come from a secrets manager / KMS, never hard-coded, never committed.
• Credentials are hashed, not encrypted — see secure-access-control (access.authn) for password hashing; this skill is for data you must later read back.

# ✅ field-level encryption at rest with a KMS-managed key
from cryptography.fernet import Fernet
cipher = Fernet(kms.get_data_key())
record.ssn_enc = cipher.encrypt(ssn.encode())     # store ciphertext, not plaintext

Anti-patterns (do NOT do this)

requests.get(url, verify=False)                      # ❌ TLS verification disabled
fetch("http://internal.api/charge")                  # ❌ plaintext http to a remote host
new https.Agent({ rejectUnauthorized: false })       # ❌ TLS verification disabled (Node)
db.save(ssn=ssn)                                      # ❌ sensitive field stored in plaintext
key = "hardcoded-secret-key"                          # ❌ key in source

How to apply (checklist while editing)

1. Does this code cross a network or persistence boundary with sensitive data? If no → nothing.
2. In transit: enforce https/wss; never disable certificate verification.
3. At rest: encrypt sensitive fields/blobs with a vetted library; keys from KMS/secrets manager.
4. Hash (don't encrypt) passwords — defer to secure-access-control.
5. Use the platform's crypto/TLS; do not roll your own.

Why it matters

crypto.in-transit and crypto.at-rest are static code properties the Throughproof verifier detects directly (plaintext http://, disabled TLS verification, missing encryption) and maps to SOC 2 / ISO 27001 / PCI-DSS / HIPAA — deterministic evidence, no runtime marker required.