EVP_chacha20, EVP_chacha20_poly1305 - EVP ChaCha20 stream cipher

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3.5.0                                              2025-06-04                                 EVP_CHACHA20(3SSL)

       The ChaCha20 stream cipher for EVP.

       EVP_chacha20()
           The  ChaCha20  stream cipher. The key length is 256 bits, the IV is 128 bits long.  The first 64 bits
           consists of a counter in little-endian order followed by a 64 bit nonce. For example a nonce of:

           0000000000000002

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

           2a000000000000000000000000000002

       EVP_chacha20_poly1305()
           Authenticated encryption with ChaCha20-Poly1305. Like 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. See the "AEAD Interface" in EVP_EncryptInit(3) section for more information.

       EVP_chacha20, EVP_chacha20_poly1305 - EVP ChaCha20 stream cipher

       Developers should be aware of the negative performance implications of calling these  functions  multiple
       times and should consider using EVP_CIPHER_fetch(3) with EVP_CIPHER-CHACHA(7) instead.  See "Performance"
       in crypto(7) for further information.

       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.

       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.

evp(7), EVP_EncryptInit(3), EVP_CIPHER_meth_new(3)

        #include <openssl/evp.h>

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