ChaCha20 Encrypt/Decrypt

ChaCha20 is a modern stream cipher designed by Daniel J. Bernstein in 2008. It is used in TLS 1.3, SSH, and VPN protocols (WireGuard). Compared to AES, ChaCha20 is faster on devices without AES hardware acceleration (phones, older CPUs) and is resistant to timing attacks. Both are considered secure, but ChaCha20 has a simpler design that is easier to implement correctly.

ChaCha20 is a stream cipher that provides confidentiality only. ChaCha20-Poly1305 is an AEAD (Authenticated Encryption with Associated Data) construction that combines ChaCha20 for encryption with Poly1305 for authentication. AEAD ensures both confidentiality and integrity — it detects any tampering with the ciphertext. Always prefer ChaCha20-Poly1305 unless you have a specific reason to use plain ChaCha20.

XChaCha20 is an extended-nonce variant of ChaCha20 that uses a 192-bit nonce instead of the standard 96-bit nonce. The larger nonce makes it safe to use with randomly generated nonces — the probability of a nonce collision is negligible even after billions of encryptions. XChaCha20 is ideal when you cannot guarantee unique nonces through a counter or sequence.

Use a cryptographically secure random number generator to create a 256-bit (32-byte) key, then encode it as hex (64 hex characters). Never reuse the same key with the same nonce — each encryption must use a unique nonce. For key derivation from a password, use PBKDF2, Argon2, or scrypt first, then use the derived key with ChaCha20.

No. All encryption and decryption happens locally in your browser using the @noble/ciphers library. Your key, nonce, and data never leave your device. This tool has no backend server — it is a pure client-side application.

Both encode the same encrypted binary data as text. Base64 is more compact (33% smaller) and commonly used in emails and web applications. Hex uses only 0-9 and A-F characters, making it easier to read and paste into code or configuration files. Choose based on your use case.

The counter is a 32-bit unsigned integer that sets the starting block number for the ChaCha20 keystream. In most cases, keep it at 0. The counter is useful when you need to encrypt multiple blocks of data separately but want them to form a continuous keystream. Both encryption and decryption must use the same counter value.

The swap button (↔) quickly switches between encrypt and decrypt modes while swapping the input and output fields. This is useful when you want to verify your encryption by immediately decrypting it, or when you paste ciphertext and want to switch to decrypt mode without manually copying and pasting.