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mukul975
70 lines
2.9 KiB
Markdown
70 lines
2.9 KiB
Markdown
---
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name: implementing-envelope-encryption-with-aws-kms
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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
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domain: cybersecurity
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subdomain: cryptography
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tags: [cryptography, encryption, aws, kms, envelope-encryption, key-management]
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version: "1.0"
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author: mahipal
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license: MIT
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---
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# Implementing Envelope Encryption with AWS KMS
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## Overview
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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.
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## Objectives
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- Understand the envelope encryption pattern and its advantages
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- Generate data encryption keys using AWS KMS GenerateDataKey
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- Encrypt/decrypt data locally using DEKs
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- Store encrypted DEK alongside ciphertext
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- Implement key caching to reduce KMS API calls
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- Handle key rotation with automatic re-encryption
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- Implement multi-region encryption for disaster recovery
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## Key Concepts
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### Envelope Encryption Flow
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1. Call `kms:GenerateDataKey` to get plaintext DEK + encrypted DEK
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2. Use plaintext DEK to encrypt data locally (AES-256-GCM)
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3. Store encrypted DEK alongside ciphertext
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4. Discard plaintext DEK from memory
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5. For decryption: call `kms:Decrypt` on encrypted DEK, then decrypt data
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### Advantages Over Direct KMS Encryption
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| Aspect | Direct KMS | Envelope Encryption |
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|--------|-----------|-------------------|
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| Max data size | 4 KB | Unlimited |
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| Latency | Network round-trip per operation | Local encryption |
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| Cost | $0.03/10,000 requests | Fewer KMS requests |
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| Offline | Not possible | Yes (with cached DEKs) |
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### KMS Key Types
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- **AWS Managed**: AWS creates and manages (`aws/s3`, `aws/ebs`)
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- **Customer Managed**: You create and manage policies
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- **Custom Key Store**: Backed by CloudHSM cluster
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## Security Considerations
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- Never store plaintext DEK; only keep encrypted DEK
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- Use key policies to restrict who can call GenerateDataKey and Decrypt
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- Enable AWS CloudTrail logging for all KMS API calls
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- Implement key rotation (automatic annual rotation for CMKs)
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- Use encryption context for authenticated encryption metadata
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- Handle KMS throttling with exponential backoff
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## Validation Criteria
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- [ ] GenerateDataKey returns plaintext and encrypted DEK
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- [ ] Data encrypts correctly with plaintext DEK using AES-256-GCM
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- [ ] Encrypted DEK can be decrypted via KMS Decrypt API
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- [ ] Decrypted DEK recovers the original data
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- [ ] Plaintext DEK is wiped from memory after use
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- [ ] Encryption context is validated during decryption
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- [ ] Key rotation re-encrypts DEKs with new master key
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