[zeugma]

However, I notice that the 512 bit key of this antique system still requires around seven hours to break. . . and that means the user would have to remain connected to the malicious website for more than seven hours for the hacker to gain access and get any information. How many of us stay on any website except perhaps FreeRepublic for more then seven hours at a time?

If they capture the packets, they can crack the key and replay the session at their leisure.

[Swordmaker]

If they capture the packets, they can crack the key and replay the session at their leisure.

That will only help them get what you were doing at the time.. . not break into your device.