Encrypt a secret message
plaintext = Hello, World!
Result: Ciphertext, nonce, tag, and the key used for decryption.
AES-GCM Encrypt
Encrypt text using AES-256-GCM, the recommended authenticated encryption algorithm. AES-GCM provides both confidentiality (encryption) and integrity (authentication) - if the ciphertext is tampered with, decryption fails. A unique 12-byte nonce is generated for each encryption. Everything runs in your browser using the Web Crypto API.
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
What is AES-GCM?
AES-GCM (Galois/Counter Mode) is an authenticated encryption algorithm. It encrypts data (confidentiality) and generates an authentication tag (integrity). If the ciphertext or tag is modified, decryption fails - detecting tampering.
What is a nonce?
A nonce (number used once) is a unique random value for each encryption. AES-GCM requires a unique nonce for each encryption with the same key. Reusing a nonce with the same key completely breaks security. This tool generates a cryptographically random 12-byte nonce for each encryption.
What is Additional Authenticated Data (AAD)?
AAD is data that is authenticated (tamper-detected) but not encrypted. It's useful for binding context to the ciphertext - e.g., including a message ID or recipient identifier that must match during decryption.
Is my data sent to a server?
No. Encryption happens entirely in your browser using the Web Crypto API. The plaintext, key, ciphertext, and nonce never leave your device.
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Generate cryptographically secure nonces for AES-GCM encryption.
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Encrypt text with AES-256-GCM - the recommended encryption standard.
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