How to install iOS 8 Beta without UDID registration :
Step 1: Connect your iDevice with iTunes via USB.
Step 2: Restore your iPhone, iPad or iPod touch to iOS 7.1.1 via iTunes, then setup it as a new iPhone
Step 3: Download iOS 8 Beta 1 for your iPhone, iPad or iPod touch
Step 4: Now your are requested to hold SHIFT and left click on “Check for Updates” on iTunes, then select iOS 8 beta 1 which you downloaded on Step 3, wait for few minutes and enjoy iOS 8
Download Here
iPhone 5s (Model A1453, A1533) - LINK
iPhone 5s (Model A1457, A1518, A1528, A1530) - LINK
iPhone 5c (Model A1456, A1532)
iPhone 5c (Model A1507, A1516, A1526, A1529) - LINK
iPhone 5 (Model A1428) - uploaded 20%
iPhone 5 (Model A1429) - LINK
iPhone 4s - LINK