implementing-envelope-encryption-with-aws-kms

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"]

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

1. Call kms:GenerateDataKey to get plaintext DEK + encrypted DEK
2. Use plaintext DEK to encrypt data locally (AES-256-GCM)
3. Store encrypted DEK alongside ciphertext
4. Discard plaintext DEK from memory
5. 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