AES Encryption Tool

Encrypted the text with AES-256-GCM (raw key).

How it works

• Used the supplied 32-byte key.
• Generated a 12-byte nonce (or used the supplied IV).
• Encrypted the UTF-8 plaintext with AES-256-GCM, producing ciphertext and a 16-byte tag.
• Encoded the ciphertext and tag together as base64 and reported the salt and IV.

• GCM is authenticated encryption: a wrong key, salt, IV or a modified ciphertext fails closed.
• The passphrase, key and plaintext stay in your browser and are never sent or stored.

Methodology

1. Derive a 256-bit key either from a raw 32-byte key or by stretching the passphrase with PBKDF2-HMAC-SHA-256 (RFC 8018) and a random salt.
2. Generate a fresh 12-byte nonce per message; a 96-bit nonce is the recommended GCM size.
3. Encrypt with AES-256-GCM per FIPS 197 and NIST SP 800-38D, producing ciphertext and a 128-bit authentication tag.
4. On decryption, recompute the tag and compare before returning any plaintext, so tampering fails closed.
5. Prefer the platform Web Crypto implementation in the browser; the bundled core matches the NIST vectors and is the deterministic fallback.

Usage

1. Choose encrypt or decrypt.
2. Enter a passphrase (and, for decryption, the salt and IV the sender provides) or a raw 32-byte key in hex.
3. Run the tool and copy the base64 ciphertext plus the IV and salt; the recipient needs all three.

Examples

These are examples, not current values: they use fixed inputs, while the interactive tool computes live results in your browser.

Encrypt with a raw AES-256 key

{
  "mode": "encrypt",
  "plaintext": "attack at dawn",
  "keyHex": "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
  "ivHex": "000102030405060708090a0b"
}

Decrypt that message

{
  "mode": "decrypt",
  "ciphertext": "JnaieqaO4nr5YfPqxodKZF6OIKVODqOj4nIkfxKE",
  "keyHex": "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
  "ivHex": "000102030405060708090a0b"
}

Encrypt with a passphrase (reproducible)

{
  "mode": "encrypt",
  "plaintext": "secret note",
  "passphrase": "correct horse battery staple",
  "saltBase64": "c2FsdHktc2FsdHktc2E=",
  "ivHex": "0f0e0d0c0b0a090807060504",
  "iterations": 1000
}

Limitations

Authenticated encryption matters

AES-GCM combines confidentiality with a tag that detects tampering. That is why a wrong key, a changed ciphertext or a reused IV fails closed instead of returning plausible garbage. Use an authenticated mode rather than AES-CBC plus a separate hash.

The one rule that must never be broken is nonce uniqueness: never reuse an IV with the same key. This tool generates a fresh IV for every interactive encryption and exposes the IV only so a recipient can decrypt.

What this tool will not do

It is not a file vault, a key manager or a secure messenger. It encrypts text you paste and hands back a value you must store safely; key management, transport security and endpoint trust remain yours.