Secure access to shared resources is one of the most challenging issues for grid development.

To ensure secure access, grid developers and users need to manage three important things:

• Access policy - What is shared? Who is allowed to share? When can sharing occur?
• Authentication - How do you identify a user or resource?
• Authorization -How do you determine whether a certain operation is consistent with the rules?

Grids need to efficiently track of all this information, which may change from day to day. This means that grids need to be extremely flexible, and have a reliable accounting mechanism. Ultimately, such accounting will be used to decide pricing policies for using the grid.

These challenges are not new - the same questions arise whenever you use your credit card in a café. But the Grid involves shared resources and so requires new solutions. Imagine if the owner of a café were to lend some tables to another café...How would you securely track customers, orders and payments?

Behind all these issues of trust there is the underlying issue of security. You may trust the other users, but do you trust that your data and applications are protected over the Internet or on other computer resources? Without adequate security, someone could read or modify your data - hence the warnings you get about security everytime you use your credit card on the Internet.

Many people are working to find a solution to these issues, many of which concern all Information Technologies and not just grids. New solutions are constantly being developed, including sophisticated data encryption techniques. But it is a never-ending race to stay ahead of malicious hackers.