Replace SHA256 with SIPHASH24 in HMAC cookie approach

Replace SHA256 with SIPHASH24 in HMAC cookie approach

Using SHA256 for this is overkill since we only need a 64bit hash
value that is not predictable. Siphash24 also fulfils these
requirements while being much faster.

Change-Id: I3b6bb178ffb2bb49981bc23eabf04fe8e06d6fc3
Signed-off-by: Arne Schwabe <arne-openvpn@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1827
Message-Id: <20260813170211.29576-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg38316.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>