RewriteEngine On

RewriteCond %{QUERY_STRING} !^access_key=my-password$ [NC]
RewriteCond %{HTTP_COOKIE} !access_key=my-password
RewriteRule ^ - [R=511,L]

Header set Set-Cookie "access_key=my-password; path=/; Max-Age=3600; HttpOnly; Secure; SameSite=Strict"