| name | implementing-envelope-encryption-with-aws-kms |
| description | Envelope encryption is a strategy where data is encrypted with a data encryption key (DEK), and the DEK itself is encrypted with a master key (KEK) managed by AWS KMS. This approach allows encrypting |
| domain | cybersecurity |
| subdomain | cryptography |
| tags | ["cryptography","encryption","aws","kms","envelope-encryption","key-management"] |
| version | 1.0 |
| author | mahipal |
| license | Apache-2.0 |
| nist_csf | ["PR.DS-01","PR.DS-02","PR.DS-10"] |
| mitre_attack | ["T1600","T1573","T1553","T1078.004","T1530"] |
Implementing Envelope Encryption with AWS KMS
Overview
Envelope encryption is a strategy where data is encrypted with a data encryption key (DEK), and the DEK itself is encrypted with a master key (KEK) managed by AWS KMS. This approach allows encrypting large volumes of data locally while keeping the master key secure in a hardware security module (HSM) managed by AWS. This skill covers implementing envelope encryption using AWS KMS GenerateDataKey API.
When to Use
- When deploying or configuring implementing envelope encryption with aws kms capabilities in your environment
- When establishing security controls aligned to compliance requirements
- When building or improving security architecture for this domain
- When conducting security assessments that require this implementation
Prerequisites
- Familiarity with cryptography concepts and tools
- Access to a test or lab environment for safe execution
- Python 3.8+ with required dependencies installed
- Appropriate authorization for any testing activities
Objectives
- Understand the envelope encryption pattern and its advantages
- Generate data encryption keys using AWS KMS GenerateDataKey
- Encrypt/decrypt data locally using DEKs
- Store encrypted DEK alongside ciphertext
- Implement key caching to reduce KMS API calls
- Handle key rotation with automatic re-encryption
- Implement multi-region encryption for disaster recovery
Key Concepts
Envelope Encryption Flow
- Call
kms:GenerateDataKey to get plaintext DEK + encrypted DEK
- Use plaintext DEK to encrypt data locally (AES-256-GCM)
- Store encrypted DEK alongside ciphertext
- Discard plaintext DEK from memory
- For decryption: call
kms:Decrypt on encrypted DEK, then decrypt data
Advantages Over Direct KMS Encryption
| Aspect | Direct KMS | Envelope Encryption |
|---|
| Max data size | 4 KB | Unlimited |
| Latency | Network round-trip per operation | Local encryption |
| Cost | $0.03/10,000 requests | Fewer KMS requests |
| Offline | Not possible | Yes (with cached DEKs) |
KMS Key Types
- AWS Managed: AWS creates and manages (
aws/s3, aws/ebs)
- Customer Managed: You create and manage policies
- Custom Key Store: Backed by CloudHSM cluster
Security Considerations
- Never store plaintext DEK; only keep encrypted DEK
- Use key policies to restrict who can call GenerateDataKey and Decrypt
- Enable AWS CloudTrail logging for all KMS API calls
- Implement key rotation (automatic annual rotation for CMKs)
- Use encryption context for authenticated encryption metadata
- Handle KMS throttling with exponential backoff
Validation Criteria
