The ChaCha20 stream cipher. 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:
000000000000000000000002
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.
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.
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