Few days ago, we got a great news from the MuscleNerd, he said that the legal Siri can be extracted from the new iOS 5.1, In other words, the operation of extracting Siri port file no longer infringe Apple’s copyright, has been legalized. So that we can port Siri on iPhone 4 or other older devices from iPhone 4S.
The message from JailbreakNation site, the developers @MrAjsTech and @leftyfl1p legally port Siri to the iPhone 4. They named this Siri port project as: i4Siri, which allows you to install Siri on iPhone 4, 3GS, iPad 1 and iPod touch 4G using Spire and proxy server technique. i4Siri is now finally available for free. i4Siri is NOT a Siri port on your older device. i4Siri is a smart Siri server which needs Siri to be ported on your device first. You will need Spire before you could get it to work with i4Siri. i4Siri servers now available to the public for free and it doesn’t require you to have a registered iPhone 4S.
How to install Siri on iPhone 4, 3GS iPad 1 and iPod Touch
Step 2: Once jailbroken, launch Cydia, tap on Search tab, search Spire and install it
Step 3: Navigate to the Settings app and head to General> Siri is, and turn Siri is on.
Step 4: Go back to Settings.app and Spire configuration, add following Siri proxy URL:
Step 5: Launch Safari browser on your idevice and navigate to http://i4siri.com/installcertificate.html then install the certificate.