Encrypt with generated key
plaintext = Top secret message
Result: Ciphertext, nonce, tag, and the 256-bit key.
AES-256-GCM Encrypt
Encrypt text using AES-256-GCM, the gold standard for authenticated encryption. AES-256 provides a 256-bit key space (2^256 possible keys), making brute-force attacks computationally infeasible. GCM mode adds authentication, detecting any tampering with the ciphertext.
Privacy: this tool processes your data entirely in your browser. Nothing you paste or type is sent to the server.
Enter your values and press Calculate — the result appears here.
Worked examples
Frequently asked questions
Why AES-256 specifically?
AES-256 is recommended by NIST, NSA (for TOP SECRET), and OWASP. The 256-bit key provides a security margin far beyond any known or projected attack. While AES-128 is also secure, AES-256 is the conservative choice for long-term security.
How do I save the key?
Copy the key immediately after encryption. It is shown once and never stored. For production use, store the key in a secure key management system (KMS) or hardware security module (HSM).
What is the output format?
The output is: ciphertext (hex), nonce (24 hex chars), and authentication tag (32 hex chars). All three are needed for decryption. The nonce and tag are not secret - they can be stored alongside the ciphertext.
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