iPhone restore from encrypted backup - just one file

[wavedave]

I had to restore iphone 4 as a new phone to fix some system issues.
it also wiped all data from any apps I had when it reinstalled them
I do not want to restore the old backup because that had the system errors
I do want to get one database off the old backup, but the backup is encrypted.
is there any way to unencrypt the backup on my mac without restoring it to the phone? I am guessing I could find the db file and manually put it on the phone.

thanks