According to recent tweets published by P0sixninja, leader of the Chronic Dev Team and 10n1c, creator of Antid0te, a tool that can improve the safety of jailbroken devices,
Apple may have implemented the system within ASLR iOS 4.3 to improve the safety and hinder the jailbreak.
The news was confirmed by Pod2G, who is working well with P0sixninja in order to release new tool to Jailbreak untethered iOS 4.2.1 which states that this move by Apple - or the introduction of the protocol ASLR - marks a turning point for both Safety device IOS, the hacker who now will have to get around much more complex and sophisticated systems to run third-party code.
The protocol ASLR involves, in essence, a different internal management of some important system libraries that makes the process of hacking much more complex. In concrete terms, your iPhone will be much safer.
This move would then make the release of Antid0te completely useless. However, the developer reserves the right to perform additional tests on iOS 4.3 once it is out of beta.