This assumes that the password derivation process is not flawed in some way. But with two PC that's only 25 million years.

You're in for 10 20*0.5/32000 seconds, also known as 50 million years. With ten random characters chosen uniformly among the hundred-of-so of characters which can be typed on a keyboard, there are 10 20 potential passwords, and brute force will, on average, try half of them. With a quad-core recent PC (those with the spiffy AES instructions), you should be able to test about 32000 potential passwords per second. The default number of iterations is 6000, so that's 12000 AES invocations for processing one password (encryption is done on a 256-bit value, AES uses 128-bit blocks, so there must be two AES invocations at least for each round).

I do not know your reasoning behind choosing KeePass (I personally prefer it), but it sounds like your needs could be better met using LastPass that has sharing features built in.KeePass uses a custom password derivation process which includes multiple iterations of symmetric encryption with a random key (which then serves as salt), as explained there.

Hope you find this approach as useful as I did.

Now, when you want to open the shared database, mark the entry and press CTRL + U.

On the advanced tab create a field named DbPath and with the value of where the shared database is located.

Create an entry in your personal database with the Password for the shared database.

This process is then simplified further by this neat 'trick' I found on the KeePass forum (slightly modified/improved): This allows us to have a very secure password on our shared databases, but also requires that the different users also use secure passwords for their private databases. All users are then required to have a personal KeePass database wherein the key to the shared databases are stored. I work voluntarily on various IT related projects, where we are groups of people that share passwords, and the different groups all share their own KeePass databases via Dropbox.

Kdbx database