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What Is AES Encryption

AES (Advanced Encryption Standard) is the most widely used symmetric encryption algorithm. Adopted by NIST in 2001, it remains the gold standard for government, banking, and enterprise systems worldwide.

Symmetric encryption means the same key is used for both encryption and decryption — anyone with the key can encrypt and decrypt data. Ready to try it yourself? Our free AES encrypt/decrypt tool runs AES-GCM entirely in your browser.

Core AES Parameters

| Parameter | Description | Common Values | |-----------|-------------|---------------| | Key length | Determines security | 128 / 192 / 256 bits | | Block size | Fixed at 128 bits | 16 bytes | | Mode | How blocks are processed | ECB / CBC / GCM / CTR | | Padding |补充 for short blocks | PKCS7 / Zero |

AES-GCM: The Recommended Mode

AES-GCM (Galois/Counter Mode) is the currently recommended mode because it provides Authenticated Encryption:

• Confidentiality: Encrypted data cannot be read
• Integrity: Data tampering is detected
• Authenticity: Data source is verified

Ciphertext = AES-GCM-Encrypt(Key, Plaintext, IV, AAD)
Plaintext = AES-GCM-Decrypt(Key, Ciphertext, IV, AAD)

Why Not ECB Mode

ECB (Electronic Codebook) is the simplest mode but has critical security flaws: identical plaintext blocks encrypt to identical ciphertext blocks, preserving data patterns.

PBKDF2 Key Derivation

Using a user password directly as an AES key is insecure because passwords are rarely random enough. PBKDF2 (Password-Based Key Derivation Function 2) derives secure keys through:

1. Password + Salt: Random salt prevents rainbow table attacks
2. Multiple iterations (e.g., 100,000): Increases brute-force cost
3. Fixed-length output: Derives the 256-bit key needed for AES-256

How to Use an Online AES Encryption Tool

Using DevToolkit Pro's AES Encrypt/Decrypt Tool:

Encrypt

1. Enter plaintext data
2. Enter a passphrase
3. Choose key length (128 / 192 / 256 bits)
4. Click Encrypt
5. Copy the resulting ciphertext (Base64 encoded)

Decrypt

1. Enter ciphertext (Base64 encoded)
2. Enter the passphrase
3. Select the matching key length
4. Click Decrypt
5. The plaintext appears in the output area

AES in Programming Languages

JavaScript / Web Crypto API

async function encrypt(data, password) {
  const encoder = new TextEncoder();
  const salt = crypto.getRandomValues(new Uint8Array(16));
  const iv = crypto.getRandomValues(new Uint8Array(12));
  
  const keyMaterial = await crypto.subtle.importKey(
    'raw', encoder.encode(password),
    'PBKDF2', false, ['deriveKey']
  );
  const key = await crypto.subtle.deriveKey(
    { name: 'PBKDF2', salt, iterations: 100000, hash: 'SHA-256' },
    keyMaterial,
    { name: 'AES-GCM', length: 256 },
    false, ['encrypt']
  );
  
  const ciphertext = await crypto.subtle.encrypt(
    { name: 'AES-GCM', iv },
    key, encoder.encode(data)
  );
  
  return { ciphertext, salt, iv };
}

Python

from cryptography.hazmat.primitives.ciphers.aead import AESGCM
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
import os

def encrypt(plaintext: str, password: str) -> bytes:
    salt = os.urandom(16)
    iv = os.urandom(12)
    
    kdf = PBKDF2HMAC(algorithm=hashes.SHA256(), length=32,
                      salt=salt, iterations=100000)
    key = kdf.derive(password.encode())
    
    aesgcm = AESGCM(key)
    return aesgcm.encrypt(iv, plaintext.encode(), None)

Security Best Practices

1. Never implement your own encryption: Use audited standard libraries (Web Crypto API, OpenSSL, BoringSSL)
2. Random IV for every encryption: Even encrypting the same content produces different ciphertext with different IVs
3. Separate key and ciphertext storage: Keys in key management services, ciphertext in databases
4. Use authenticated encryption: Prefer AES-GCM over AES-CBC

FAQ

How Much More Secure Is AES-256 vs AES-128?

Practically, both are sufficiently secure. AES-128's key space is 2^128 — brute-forcing it would take longer than the universe's age. AES-256 provides a larger security margin and is the choice for government-grade applications.

Are Online AES Tools Secure?

DevToolkit Pro's AES tool runs entirely in the browser via the Web Crypto API — passwords and data never leave your device. However, ensure you're in a secure environment and be aware of browser extensions that might access your data.

Does Encryption Increase Data Size?

Slightly. AES-GCM output includes ciphertext + authentication tag (16 bytes) + IV (12 bytes). The overhead ratio is higher for small data but negligible for large data.

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