Unable to open Xcode 7.3.1 and Xcode 6.4 on macOS Sierra (10.12.1).

I downloaded both Xcode 7.3.1 & Xcode 6.4 .dmg files from https://developer.apple.com/downloads/more and opened it and copied to Applications. But when I open it, it go for verification of the identity of developer. But after some time, it shows "Unable to verify the identity of the developer" and get closed. I redownloaded the .dmg files again and tried once more. But the result was same. There is no problem with Xcode 8.1 downloaded from Mac AppStore, but I need Xcode 6.4 & Xcode 7.3.1, is there any solution?