|Initial release||October 12, 2011|
|Operating system||iOS, OS X|
|Type||Instant messaging service|
iMessage is an instant messenger service developed by Apple Inc. It is supported by the Messages application in iOS 5 and later and OS X Mountain Lion and later. Andrew Vyrros is the lead developer.
iMessage was announced by Scott Forstall at the WWDC 2011 keynote on June 6, 2011. A version of the iOS Messages application with support for iMessage was included in the iOS 5 update on October 12, 2011.
On February 16, 2012, Apple announced that a new OS X Messages application with support for iMessage, replacing iChat, would be part of OS X Mountain Lion. Mountain Lion, with Messages, was released on July 25, 2012.
On October 23, 2012, Apple CEO, Tim Cook announced that Apple device users have sent 300 billion messages using iMessage and that Apple delivers an average of 28,000 messages per second.
On November 12, 2012, Chetan Sharma, a technology and strategy consulting firm, published the US Mobile Data Market Update Q3 2012, noting the decline of text messaging in the United States, and suggested the decline may be attributed to Americans using alternative free messaging services such as iMessage.
iMessage allows users to send texts, documents, photos, videos, contact information, and group messages over Wi-Fi, 2G, 3G or LTE to other iOS or OS X users, thus providing an alternative to standard SMS/MMS messaging for most users with devices running iOS 5 or later.
iMessage is accessible through the Messages app on an iPhone, iPad or iPod touch running iOS 5 or later or on a Mac running OS X Mountain Lion or later. Owners of these devices can register one or more email addresses with Apple, and, additionally, iPhone owners can register their phone numbers with Apple, provided their carrier is supported. For iPhone users who have an active data connection, Messages will check with Apple if the recipient has iMessage set up. If they do, it will seamlessly transition from SMS to iMessage.
In Messages, the user's sent communication is aligned to the right, with replies from other people on the left. A user can see if the other iMessage user is typing a message, pale gray ellipsis appears in the text bubble of the other user when a reply is started. It is also possible to start a conversation on one iOS device and continue it on another. iMessage-specific functions operate only between machines running iOS 5 or later or running Mountain Lion or later, but, on the iPhone, Messages can use SMS to communicate with non-iOS devices, or with other iPhones when iMessage is unavailable. On iPhones, green buttons and text bubbles indicate SMS-based communication; on all iOS devices, blue buttons and text bubbles indicate iMessage communication.
All iMessages are encrypted and can be tracked using delivery receipts. If the recipient enables Read Receipts, the sender will be able to see that the recipient has read the message.
iMessage also allows users to set up chats with more than two people - a "group chat". However, the group chatting features do not integrate very well with members in the group who have a different type of phone.
If the iPhone is running iOS 5 or greater, the messaging app will send text messages as an iMessage instead of the usual text message. This means that if you are sending text messages with another iOS 5 user, there is no SMS charge associated with the messaging. It is merely treated as an additional data transfer.
iMessage is very similar to MMS: it not only allows the user to send plain text, but also allows the user to send pictures, movies, locations, and contacts.
Just like APNS it sets up a Keep-Alive connection with the Apple servers. Every connection has its own unique code, which acts as an identifier for the route that should be used to send a message to a specific device. The connection is encrypted with TLS using a client side certificate, that is requested by the device on the activation of iMessage.
Apple says that iMessages are protected by end-to-end encryption "so no one but the sender and receiver can access them" and Apple assures that "[they] cannot decrypt the data" and "[they do] not log messages".
||This article reads like an editorial or opinion piece. (June 2014)|
We[who?] carelessly use Apple's iMessage to share our photos and videos with our friends and family from all of our Apple devices. Mark Zuckerberg told his audience in 2010 that "people have really gotten comfortable not only sharing more information and different kinds, but more openly and with more people". We assume that all our media content and text content on iMessage is secured and safe but the question is - is it ?
"After the revelations made about NSA’s PRISM program by Edward Snowden in June, Apple claimed that conversations taking place over iMessage and FaceTime “are protected by end-to-end encryption, so no one but the sender and receiver can see or read them. Apple cannot decrypt that data. Similarly, we do not store data related to customers’ location, map searches or Siri requests in any identifiable form.”" 
However "[s]ecurity experts have long suspected that iMessage is not as safe and impenetrable as Apple claims."  "Researchers claim that "Apple can read your iMessages if they chose to, or if they are required to do so by a government order". "The weakness is in the [encryption] key infrastructure as it is controlled by Apple: they can change a key anytime they want, thus read the content of our iMessages.”" 
"iMessage uses public-private key encryption systems. That means that a public key for a user is stored on Apple's server, and a private key on each device linked to their account. The private- public key pair is generated when the user creates an iCloud account with Apple. When someone chooses an addressee for an iMessage, the recipient's public key - which works like a padlock - is retrieved from Apple's servers and used to encrypt the message. That can in theory only be unlocked by the private key held by the recipient. Messages sent to multiple recipients are encrypted using those recipients' public keys. But Quarkslab says that Apple’s management of the initial security key is obfuscated – and so it is impossible for the user to know if messages are being sent to a third party such as the NSA." 
The real issue at hand is "the inappropriateness of the flow of information due to the mediation of technology. Privacy violations occur not when too much data accumulates or people can't direct it, but when one of the receivers or transmission principles change". 
One of the best ways to resolve this issue and to restore trust in the media content sharing community, is to have Apple sent out a clear explicit notification from the iMessage services would suffice. "[By letting] companies [like Apple] do standard data collection but [asking] them to tell people when they are doing things with data that are inconsistent with the "context of the interaction" between a company and a person" might be an appropriate solution.  Apple is known for its stringent measures when it comes to user privacy. And we, the users, hope that it takes a similar stance when it comes to secured connectivity via iMessages.
Multiple news reporters have verified allegations that if a user switches from an Apple device to a non-Apple device, SMS messages being delivered to them through iMessage will not reach their destination. A lawsuit has been filed against Apple over this issue.
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- Messages (application)
- Apple Push Notification Service
- Microsoft Messenger service
- Google Cloud Messaging