EVP_CHACHA20(3ossl)

💅 EVP_CHACHA20 💅

okay so this is the EVP_CHACHA20(3ossl) page from the OpenSSL manual, and bestie, it's literally all about the ChaCha20 stream cipher and its poly1305 glow-up. stay with me, it's gonna slay. ✨

---

🌸 NAME 🌸

EVP_chacha20, EVP_chacha20_poly1305 — the EVP ChaCha20 stream cipher, no cap 🫶

---

🎀 SYNOPSIS 🎀

#include <openssl/evp.h>

const EVP_CIPHER *EVP_chacha20(void);
const EVP_CIPHER *EVP_chacha20_poly1305(void);

---

🦋 DESCRIPTION 🦋

It's the ChaCha20 stream cipher, but for EVP. iconic behavior honestly 💅

⭐ EVP_chacha20()

The ChaCha20 stream cipher, periodt. The key length is 256 bits, and the IV is 128 bits long. The first 64 bits is a counter in little-endian order, followed by a 64 bit nonce. so like, for example, a nonce of:

0000000000000002

with an initial counter of 42 (2a in hex) would be expressed as:

2a000000000000000000000000000002

like, that's the whole vibe. the counter goes first, little-endian, then the nonce. 🧚

👑 EVP_chacha20_poly1305()

Authenticated encryption with ChaCha20-Poly1305 — it's giving main character energy fr fr. Like EVP_chacha20(), the key is 256 bits, and the IV is 96 bits. This one supports additional authenticated data (AAD) and produces a 128-bit authentication tag. See the "AEAD Interface" in EVP_EncryptInit(3) section for more info. 🎀

---

💀 NOTES 💀

Developers, listen up bestie: there are negative performance implications of calling these functions multiple times 😭. Consider using EVP_CIPHER_fetch(3) with EVP_CIPHER-CHACHA(7) instead. See "Performance" in crypto(7) for further information.

also, fun fact: RFC 7539 <https://www.rfc-editor.org/rfc/rfc7539.html#section-2.4> uses a 32 bit counter and a 96 bit nonce for the IV. just so you know the vibes are different there 👀

---

✨ RETURN VALUES ✨

These functions return an EVP_CIPHER structure that contains the implementation of the symmetric cipher. See EVP_CIPHER_meth_new(3) for details of the EVP_CIPHER structure. slay. 🫶

---

🌈 SEE ALSO 🌈

• evp(7)
• EVP_EncryptInit(3)
• EVP_CIPHER_meth_new(3)

---

🍓 COPYRIGHT 🍓

Copyright 2017-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

---

and that's the whole page, bestie — this version is 3.5.0, dated 2026-09-25, from the 3ossl manual. go forth and encrypt iconically 💖✨