ChaCha20 Decryption

ChaCha20 decryption online

Decrypt ChaCha20 or XChaCha20 ciphertext with the same 256-bit key, nonce, and counter used for encryption. This page supports text and local file input with Hex or Base64 ciphertext encodings.

How to decrypt

1. Paste ciphertext or upload a file and select the input encoding.
2. Choose ChaCha20 or XChaCha20 to match the encrypting system.
3. Enter the key and nonce, or the same KDF settings used during encryption.
4. Set Counter if the peer started at a non-zero block counter.
5. Decrypt and inspect the plaintext encoding.

Matching parameters

ChaCha20 requires a 96-bit nonce; XChaCha20 requires a 192-bit nonce. Wrong keystream parameters produce incorrect plaintext without an authentication failure. Use ChaCha20-Poly1305 decryption when the ciphertext includes a Poly1305 tag.

Frequently asked questions

Why is the plaintext garbled?

Confirm algorithm, key or KDF settings, nonce, counter, salt format, and encodings. Raw ChaCha20 does not report authentication failures. OpenSSL-formatted passphrase ciphertext carries the salt in its Salted__ envelope; Format None requires the same salt to be entered separately.