Researchers reverse-engineered the language processing, interactive personal assistant application called Siri. The iPhone 4S communicates with a server at Apple over HTTPS for Siri messages, so the researchers figured out a way to take advantage of that setup. The researchers did not publish their 4S identifier (for obvious reasons) Apple could blacklist fake identifiers, but they contend this is unlikely if you are running the application for personal use. If you actually want to install Siri on your non-4S device you ll still need an 4S ID.
Source: https://threatpost.com/researchers-crack-siri-protocol-111511/75896/