This is the entry in the nginx.conf which is using proxy cache . I dont see any option here to configure hashing algorithm

location /nginx-picture {
internal;
proxy_buffering on;
proxy_cache media;
proxy_cache_key $uri$args;
proxy_cache_valid 200 43200s;
proxy_ignore_headers Expires;
proxy_ignore_headers Cache-Control;
add_header X-Cache-Status $upstream_cache_status;
proxy_pass http://acs_backend$request_uri;
}