| name | implementing-aes-encryption-for-data-at-rest |
| description | Guides implementing AES-256 encryption in GCM mode (FIPS 197) for files and data stores at rest, covering key derivation, IV/nonce management, and authenticated encryption. Use when deploying or configuring encryption for data at rest, establishing controls to meet compliance requirements, or reviewing an implementation during a security assessment. |
| domain | cybersecurity |
| subdomain | cryptography |
| tags | ["cryptography","encryption","aes","data-at-rest","symmetric-encryption"] |
| 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","T1486"] |
Implementing AES Encryption for Data at Rest
Overview
AES (Advanced Encryption Standard) is a symmetric block cipher standardized by NIST (FIPS 197) used to protect classified and sensitive data. This skill covers implementing AES-256 encryption in GCM mode for encrypting files and data stores at rest, including proper key derivation, IV/nonce management, and authenticated encryption.
When to Use
- When deploying or configuring implementing aes encryption for data at rest 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
- Implement AES-256-GCM encryption and decryption for files
- Derive encryption keys from passwords using PBKDF2 and Argon2
- Manage initialization vectors (IVs) and nonces securely
- Encrypt and decrypt entire directory trees
- Implement authenticated encryption to detect tampering
- Handle large files with streaming encryption
Key Concepts
AES Modes of Operation
| Mode | Authentication | Parallelizable | Use Case |
|---|
| GCM | Yes (AEAD) | Yes | Network data, file encryption |
| CBC | No | Decrypt only | Legacy systems, disk encryption |
| CTR | No | Yes | Streaming encryption |
| CCM | Yes (AEAD) | No | IoT, constrained environments |
Key Derivation
Never use raw passwords as encryption keys. Always derive keys using:
- PBKDF2: NIST-approved, widely supported (minimum 600,000 iterations as of 2024)
- Argon2id: Winner of Password Hashing Competition, memory-hard
- scrypt: Memory-hard, good alternative to Argon2
Nonce/IV Management
- GCM requires a 96-bit (12-byte) nonce that must NEVER be reused with the same key
