Comment en Utiliser ChaCha20 Chiffrement

问题

You besoin un rapide, sûr stream chiffre ce fait non require hardware AES acceleration, such comme sur mobile ou IoT devices.

Prérequis

• Understanding of stream ciphers
• Knowledge of authenticated encryption

Étapes

1. 1. Generate a key and nonce

   ChaCha20 uses a 256-bit key and a 96-bit nonce (when used with Poly1305). Generate both using a CSPRNG. The nonce must be unique per key, just like in GCM.

   entrée

   256-bit key + 96-bit nonce

   输出

   32 + 12 random bytes

2. 2. Encrypt with ChaCha20-Poly1305

   Use the authenticated ChaCha20-Poly1305 construction rather than raw ChaCha20. Poly1305 provides integrity, preventing ciphertext tampering. The cipher produces ciphertext and a 128-bit authentication tag.

   entrée

   plaintext + key + nonce

   输出

   ciphertext + tag

3. 3. Verify the tag on decryption

   On decryption, verify the Poly1305 tag before using the plaintext. If the tag does not match, reject the data. This prevents using tampered or corrupted ciphertext.

   entrée

   ciphertext + tag + key

   输出

   plaintext (if tag valid)

Résultat attendu

Rapide authenticated chiffrement suitable pour environments sans AES hardware acceleration.

Erreurs courantes

Using raw ChaCha20 without Poly1305

Raw ChaCha20 provides no integrity. Always use ChaCha20-Poly1305 for authenticated encryption.

Reusing the nonce

Like GCM, nonce reuse in ChaCha20-Poly1305 is catastrophic. Generate a unique nonce per encryption.

Dépannage指引

• If performance is the concern, ChaCha20-Poly1305 is often faster than AES-GCM on devices without AES-NI.
• ChaCha20-Poly1305 is used in TLS 1.3 and WireGuard, proving its real-world adoption.

Limites de sécurité

• ChaCha20-Poly1305 is a modern, well-analyzed cipher. Its main risk is nonce reuse, which must be prevented.
• All operations are local.