Encrypted ipa packages are not supported.
Does the subject want to ask, "What do you mean you don't support encrypted ipa packages?" The installation cannot be signed again. The Ipa file is actually a zip compressed package, which means that it cannot be signed and installed again. Ipa format is apple's exclusive software installation package launched on iOS platform, which was officially used after 2.0 firmware. It is the only official installation package on iPhone/iPodTouch/iPad platform.