BSI C5 · Control CRY-03 · Priority: critical · Component: Cryptography & Key Management

What this control covers

Encrypts stored customer data with private keys known only to customers, per legal requirements. Specifies exceptions via contractual agreements, ensuring confidentiality of cloud customer data at rest through robust encryption procedures.

Why it matters

Encryption and key management make data unreadable to attackers and unintelligible under data-breach safe-harbour clauses — a meaningful regulatory benefit.

How to implement

AWS

Default to SSE-KMS with customer-managed keys for S3/EBS/RDS/Secrets Manager. Use S3 Bucket Keys and S3 Block Public Access at the account level, and turn on S3 Object Lock on backup buckets for ransomware resilience.

Azure

Store secrets in Key Vault (HSM-backed where required) with soft-delete + purge protection; use customer-managed keys for Storage, SQL, and Azure Disk Encryption. Tag PII data via Microsoft Purview.

GCP

Use Cloud KMS with customer-managed encryption keys (CMEK) for BigQuery, GCS, and Compute. Sensitive Data Protection (DLP API) inspects/de-identifies PII at scale.

Google Workspace

Enable client-side encryption for Drive/Docs and turn on Drive Labels + DLP rules to prevent external sharing of regulated data classes.

Evidence to collect

  • infra_scan — See the iCompaas Evidence library for the canonical source for this evidence type.

Infrastructure posture tooling (AWS Config, Azure Policy, Nessus) verifies platform hardening. Focus: Encryption of sensitive data for storage.

Quick checklist

  • Exceptions — Agreements / Protection
  • Security — Agreements / Protection
  • Confidentiality — Agreements / Protection
  • Protection — Agreements / Protection
  • Data — Agreements / Protection
  • Encryption — Agreements / Protection

Related articles on this site