There is a multitude of ways to crack through network protocols such as the often deprecated WEP (Wired Equivalent Privacy) and the current WPA and WPA2 (WiFi Protected Access) standard. By design, WEP is flawed; as such, it's one of the easiest encryption protocols to hack and crack ever made. Even script kiddies (amateur hackers who use predefined scripts and readily made programs written by more competent crackers to conduct their hack attacks) are capable of cracking the WEP standard.
No matter how short, long, or disingenuous your WEP key is
It can and will be cracked, no exceptions. That's just how flawed the WEP protocol is, which is why it's practically never used save for the most obsolete of WiFi networks. In contrast, a WPA or WPA2 (the improved version of WPA) protocol has learned from WEP's notorious mistakes and is built from the ground up as a superior encryption approach that's a lot harder to crack.
A WPA or WPA2 key can be rendered impenetrable enough by simply applying basic key or password creation guidelines to help stop it from ever being cracked by any online outlaws (e.g., use both letters and numbers, use capital letters and small letters, and make the password as long as possible). Ironically, the same things that make WPA superior to WEP are what make it easier to crack in a different context.
Although the WPA standard is not as flawed as WEP such that using an Airocrack program suite is all you'll ever need to bypass it, it is still a little more cracker-friendly because it allows offline cracking once a hacker captures the correct kind of packets. Ergo, a hacker only needs to be near the access point for a few seconds to get what he needs to crack the system, thereby lowering his chances of being caught in the middle of doing a crack attempt.
More to the point, if you're a hacker attempting to crack through a WiFi network, you can use the WPA handshake as a way to crack through a WPA- or WPA2-secured wireless connection. All you'll need to do is capture the full authentication handshake from an access point and the real client in order to start your cracking tasks undisturbed and right at the comfort of your own home.
It's a lot easier said than done, though, but a bit of packet injection should help ease matters. You can even force an authentication handshake via a deauthentication attack, but you should only launch this if you're certain that the real client is already connected in order to determine which channel the WPA or WPA2 is sitting on.