.\" $OpenBSD: EVP_chacha20.3,v 1.1 2023/08/15 11:26:49 schwarze Exp $ .\" full merge up to: OpenSSL 35fd9953 May 28 14:49:38 2019 +0200 .\" .\" This file was written by Ronald Tse .\" and Matt Caswell . .\" Copyright (c) 2017, 2019 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: August 15 2023 $ .Dt EVP_CHACHA20 3 .Os .Sh NAME .Nm EVP_chacha20 , .Nm EVP_chacha20_poly1305 .Nd ChaCha20 stream cipher for EVP .Sh SYNOPSIS .In openssl/evp.h .Ft const EVP_CIPHER * .Fn EVP_chacha20 void .Ft const EVP_CIPHER * .Fn EVP_chacha20_poly1305 void .Sh DESCRIPTION .Fn EVP_chacha20 provides the ChaCha20 stream cipher in the EVP framework. The key length is 256 bits, the IV is 128 bits long. The first 32 bits consists of a counter in little-endian order followed by a 96 bit nonce. For example a nonce of: .Pp 000000000000000000000002 .Pp With an initial counter of 42 (2a in hex) would be expressed as: .Pp 2a000000000000000000000000000002 .Pp .Fn EVP_chacha20_poly1305 provides authenticated encryption with ChaCha20-Poly1305. Like .Fn EVP_chacha20 , the key is 256 bits and the IV is 96 bits. This supports additional authenticated data (AAD) and produces a 128-bit authentication tag. .Sh RETURN VALUES These functions return return pointers to static .Vt EVP_CIPHER objects that contain the implementations of the symmetric cipher. .Sh SEE ALSO .Xr evp 3 , .Xr EVP_CIPHER_meth_new 3 , .Xr EVP_EncryptInit 3