Draws of investment bonds (“premium bonds”)

Here in Egypt we have something called investment bonds which are sold in the banks. They are known as “Group C” bonds, and they carry no profit, i.e., if you buy a certificate, then you want to return it, even ten years later, or more, or less, you will get back the same amount as you paid for it. Then the computer selects a number of one of the certificates that have been sold, and this wins first prize; there also second, third prizes and so on, as many as 400 prizes. The first prize is twenty thousand (Egyptian) pounds. What I want to know is, if I buy one of these bonds then I am one of the prize-winners, is it permissible for me to take this money or not? Will I be committing a sin?