Howto implement chacha20-poly1305?

[Stef Bon]

Hi,

I;m writing a fuse sftp client, and not making use of openssh (like
sshfs does). I'm writing all required procedures and functions to do
the negotiation and encryption myself, using libgcrypt.
This works already very good.
It basically uses simple encryption like 3des and blowfish and aes,
and mac like hmac-sha1 en hmac-sha256.

Now I want also support for newer algo's like chacha20-poly1305 and
poly1305-AES.

I'm asking cause I cannot find any documentation and the named algo's
are encryption and hmac combined, and this requires extra attention.

Thanks in advance,

Stef Bon
the Netherlands