Replacing key in ${QUERY_STRING} via .htaccess

Question

Hello together! Could someone please give me a tip how to replace the key in a query string but keep the value (in this case the value is allways a hash)?

Basically it want to do that:
index.php?OLDKEY=(hash) -> index.php?NEWKEY=(hash)

Right now i have something like that in my .htaccess:
RewriteCond ${QUERY_STRING} ^OLDKEY=(.*)$
RewriteRule index\.php /index.php?NEWKEY=$1
... but this does not work :/

Could someone give me a hint how i could do this?
Thanks alot!

Answer 1

... i found it out by myself. My rule looks like that:

RewriteCond %{QUERY_STRING} ^OLDKEY=([^&]*) [NC]
RewriteRule ^index\.php$ %{REQUEST_URI}?NEWKEY=%1 [L,NC,R=301]