implementing-aes-encryption-for-data-at-rest

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Implementing AES Encryption for Data at Rest

实现静态数据的AES加密

Overview

概述

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.

AES（Advanced Encryption Standard，高级加密标准）是由NIST（美国国家标准与技术研究院，FIPS 197）标准化的对称分组密码，用于保护机密和敏感数据。本技能涵盖在GCM模式下实现AES-256加密，以加密静态文件和数据存储，包括正确的密钥派生、IV/随机数（nonce）管理以及认证加密。

When to Use

使用场景

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

在您的环境中部署或配置静态数据AES加密功能时
建立符合合规要求的安全控制措施时
构建或改进该领域的安全架构时
开展需要此实现的安全评估时

Prerequisites

前置条件

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

熟悉密码学概念和工具
可访问测试或实验室环境以安全执行操作
安装了必要依赖的Python 3.8+版本
具备任何测试活动的适当授权

Objectives

目标

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

实现文件的AES-256-GCM加密和解密
使用PBKDF2和Argon2从密码派生加密密钥
安全管理初始化向量（IV）和随机数（nonce）
加密和解密整个目录树
实现认证加密以检测篡改行为
通过流式加密处理大文件

Key Concepts

核心概念

AES Modes of Operation

AES 操作模式

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

模式	支持认证	可并行化	使用场景
GCM	是（AEAD）	是	网络数据、文件加密
CBC	否	仅解密	遗留系统、磁盘加密
CTR	否	是	流式加密
CCM	是（AEAD）	否	IoT、受限环境

Key Derivation

密钥派生

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

切勿将原始密码用作加密密钥。务必通过以下方式派生密钥：

PBKDF2：NIST认可，广泛支持（截至2024年，最少600,000次迭代）
Argon2id：密码哈希竞赛获胜者，内存密集型
scrypt：内存密集型，Argon2的良好替代方案

Nonce/IV Management

Nonce/IV 管理

GCM requires a 96-bit (12-byte) nonce that must NEVER be reused with the same key
Generate nonces using
```
os.urandom()
```
(CSPRNG)
Store nonce alongside ciphertext (it is not secret)

GCM要求使用96位（12字节）的nonce，同一密钥下绝对不能重复使用
使用
```
os.urandom()
```
（密码学安全伪随机数生成器）生成nonce
将nonce与密文一起存储（它不是机密信息）

Workflow

工作流程

Install the
```
cryptography
```
library:
```
pip install cryptography
```
Generate or derive an encryption key
Create a random nonce for each encryption operation
Encrypt data using AES-256-GCM with the key and nonce
Store nonce + ciphertext + authentication tag together
For decryption, extract nonce, verify tag, and decrypt

安装
```
cryptography
```
库：
```
pip install cryptography
```
生成或派生加密密钥
为每次加密操作创建随机nonce
使用密钥和nonce通过AES-256-GCM加密数据
将nonce + 密文 + 认证标签一起存储
解密时，提取nonce、验证标签并解密

Encrypted File Format

加密文件格式

[salt: 16 bytes][nonce: 12 bytes][ciphertext: variable][tag: 16 bytes]

[salt: 16 bytes][nonce: 12 bytes][ciphertext: variable][tag: 16 bytes]

Security Considerations

安全注意事项

Always use authenticated encryption (GCM, CCM) to prevent tampering
Never reuse a nonce with the same key (catastrophic in GCM)
Use at least 256-bit keys for long-term data protection
Securely wipe keys from memory after use when possible
Rotate encryption keys periodically per organizational policy
For disk-level encryption, consider XTS mode (AES-XTS)

始终使用认证加密（GCM、CCM）以防止篡改
同一密钥下绝不能重复使用nonce（在GCM中会导致严重安全问题）
至少使用256位密钥进行长期数据保护
尽可能在使用后从内存中安全清除密钥
根据组织策略定期轮换加密密钥
对于磁盘级加密，考虑使用XTS模式（AES-XTS）