AES Encryption Guide for Developers
Encrypt and decrypt data with AES-256-GCM — key generation, IV, authentication tag, and secure usage.
Published:
Tags: AES encryption guide, AES-256 encryption, symmetric encryption developer
AES Encryption Guide for Developers Part of our complete guide to this topic — see the full series. AES-256-GCM is the standard for symmetric encryption. It provides confidentiality, integrity, and authenticity in a single operation — meaning you can detect tampering at decryption time. This guide covers the algorithm, modes of operation, key and IV management, and practical implementations in Python, Node.js, and the browser. --- What is AES Fundamentals? AES is a block cipher: it processes data in 128-bit (16-byte) blocks. Each block is transformed through a series of rounds (10 for 128-bit keys, 12 for 192-bit, 14 for 256-bit) using the key schedule. For encrypting data larger than 16 bytes, AES must be combined with a mode of operation that handles multiple blocks. What is Modes of…
Frequently Asked Questions
What is AES encryption?
AES (Advanced Encryption Standard) is a symmetric block cipher standardized by NIST in 2001. It replaced DES as the US government encryption standard. AES uses the same key for both encryption and decryption, operates on 128-bit blocks, and supports key sizes of 128, 192, or 256 bits. AES-256 provides the highest security margin and is used in TLS, disk encryption, and virtually all modern secure storage.
What is the difference between AES-CBC and AES-GCM?
AES-CBC (Cipher Block Chaining) provides confidentiality only — it encrypts data but cannot detect tampering. Without a separate MAC, CBC ciphertext is vulnerable to padding oracle attacks. AES-GCM (Galois/Counter Mode) provides authenticated encryption: it both encrypts data and generates a 128-bit authentication tag. Decryption fails if the ciphertext or tag was modified. Always prefer GCM for new implementations.
How do I generate a secure AES key?
Generate key material from a CSPRNG (cryptographically secure pseudorandom number generator). In Python: `key = os.urandom(32)` for a 256-bit key. In Node.js: `crypto.randomBytes(32)`. In the browser: `crypto.getRandomValues(new Uint8Array(32))`. Never use `Math.random()` or derive keys from predictable values like timestamps.
What is an IV (initialization vector)?
An IV (or nonce) is a random value combined with the key to ensure that encrypting the same plaintext twice produces different ciphertexts. For AES-GCM, use a 12-byte (96-bit) IV generated fresh for every encryption operation. The IV is not secret — it is typically prepended to the ciphertext for transmission. The critical rule: never reuse an IV with the same key.
How do I implement AES in JavaScript?
Use the Web Crypto API's `crypto.subtle.encrypt` with `{ name: 'AES-GCM', iv }`. Generate a key with `crypto.subtle.generateKey({ name: 'AES-GCM', length: 256 }, true, ['encrypt', 'decrypt'])`. The Web Crypto API is available in all modern browsers and Node.js 15+ without any dependencies.
All articles · theproductguy.in