How Does iMessage Work Technically Securely

How Does iMessage Work Technically Securely
Content List

Sending and receiving messages via iMessage is done securely.

iMessage users can begin a new conversation by entering a phone number or email address. In order to retrieve the public keys and APN addresses for all devices associated with an addressee, the Apple Identity Service (IDS) is contacted. To get the public keys and APN addresses associated with a given name, the device first consults the user's Contacts app, which pulls up all of the phone numbers and email addresses associated with the name entered by the user.

Each device that will be receiving the message from the sender has its own unique encryption key. IDS retrieves the public encryption and signing keys of the devices that are receiving the messages. In order to construct a 40-bit value from the sender and receiver public keys and the plaintext, the sending device generates an 88-bit random value and uses it as an HMAC-SHA256 key. The message is encrypted with AES in Counter (CTR) Mode using a 128-bit key generated by concatenating the 88-bit and 40-bit values. The receiver verifies the integrity of the decrypted plaintext using the 40-bit value. RSA-OAEP is used to encrypt this per-message AES key to the device's public key. To sign the hash, the Elliptic Curve Digital Signature Algorithm (ECDSA) uses the sending device's private signing key to hash and sign the encrypted message text and encrypted message key. Elliptic Curve Integrated Encryption Scheme (ECIES) may be used instead of RSA encryption in iOS 13 or later and iPad 13.1 and later.

The encrypted message text, the encrypted message key, and the sender's digital signature are included in each message. Deliveries to the APNs are then made. Timestamp and APN routing information are not encrypted. TLS is used to encrypt communication between APNs and their customers.

Depending on the iOS or iPadOS version, APNs can only relay messages up to 4 or 16 KB in size. Encrypted 256-bit keys are generated by using AES in CTR mode with a randomly generated message text or attachment and then uploaded to iCloud. An iMessage is then sent containing the attachment's AES key, its URI, and an SHA-1 hash of its encrypted form, all of which are protected by the standard iMessage encryption.

How Does iMessage Work Technically Securely


How iMessage sends and receives messages.

This is repeated for each participant and their device in a group conversation.

If necessary, each device retrieves the attachment from iCloud after receiving a copy of the message from APNs. Receiver contacts are matched to the sender's phone number or email so that when possible, a name can be displayed.

The message is deleted from APNs as soon as it is delivered. There are some differences between APNs notifications and iMessage notifications. Emails are kept for a period of thirty (30) days.

What exactly is iMessage? What is the procedure?

Our previous article, "iMessage frequently asked questions," was published on our website. In that article, we provided a high-level overview of the iMessage interface. More information can be found in this article. In this article, we will discuss what iMessage is, how it works, and what you can do if it is not functioning properly.

What is an iMessage, exactly?

If you want to collaborate with others, you can use iMessage. The iMessage service is a free and secure encrypted messaging service that is available for use on iPhone, iPad, Mac, and Apple Watch. Apple's own messaging service, dubbed iMessage, is available. It was first made available in 2011.

iMessage is considered an "Over The Top" (OTT) service because it does not require the use of a cellular data connection to function. Sending messages over Wi-Fi or cellular data networks will be the most convenient option for you. If Wi-Fi is not available, your message will be sent via cellular data if one is available. If you send or receive iMessages over Wi-Fi, there is no additional charge. Therefore, iMessage may consume cellular data from your phone, which will be deducted from your existing mobile data allowance. Furthermore, iMessage may consume a significant amount of data, particularly if you are sending pictures or videos via iMessage. If your cellular data plan has a limit on the amount of data you can use, the iMessages you send over cellular data do not count toward your monthly text message allowance.

Text messages (SMS or MMS) are sent and received using a cellular data plan that includes text-messaging capabilities. Text message plans are typically offered by wireless carriers in three varieties:

The plan includes unlimited texting. You have the ability to send an unlimited number of text messages, as the name suggests.

There is a limited text plan. When you have this type of plan, you have a messaging allowance, which is usually monthly, which states how many text messages you can send.

You can also pay per message. Each message that you send or receive is charged to you by your carrier.

You can send an unlimited number of iMessages, regardless of your data plan.

How to send an iMessage on an iPhone

To be able to send and receive iMessages, your device must be running iOS 5 or later, watchOS 1 or later, or OS X Mountain Lion or later, and it must have Apple's Messages app installed. To send an iMessage, both you and the recipient must have an iPhone, iPad, iPod touch, Mac, or Apple Watch that is compatible with iMessage.

Everything is carried out automatically. A two-way, iMessage-capable device is required in order to send iMessages. Simply open the Messages app on your device, type your message, and then press the Send button. After that, Messages will check with Apple servers to see if your recipient has an iMessage account. Your message will be automatically sent as an iMessage if you select this option. If you choose not to use this feature, your message will be sent as a regular text message (SMS/MMS).

Apple iMessages will be represented by blue bubbles, while regular text messages will be represented by green bubbles.

To enable or disable iMessage on your device, follow these steps:

Go to Settings > Messages and iMessage on your iPhone, iPad, or iPod touch to learn how to send an iMessage.

To turn off iMessage on your Mac, open the Messages app and go to Messages > Preferences, then click Accounts and select your iMessage account from the drop-down menu.

Features of the iMessage app

iMessage has a slew of interesting features. Text, pictures, videos, sound, location, money, heartbeats, and other types of data can be sent and received with relative ease. Here are some of the characteristics:

iMessage chats can be organized into groups. For more information, see: How To Exit A Group Message On Your iPhone.

Read receipts are included in iMessage.

In Messages, you can send photos, videos, and audio files.

You have the option of sending your location.

You have the option of using message effects.

With Digital Touch, you can send a sketch, a tap, or a heartbeat to someone.

Apple Pay allows you to send and receive money in real-time.

You can send animated GIFs by using the hashtag #images.

You can make use of iMessage applications.

Messages in Cloud allows you to keep your entire message history up to date and accessible on all of your devices at the same time.

The best way to troubleshoot iMessage issues

If you are having difficulties with iMessage, please refer to the information below:


Check to see if your device is running the most recent version of iOS, iPad OS, Mac OS, or watch OS.

Make sure your Mac is up to date.

Update the software on your iPad or iPhone.

Start by turning off iMessage (see the section above for information about how to do so), then restart your device and then turn back on iMessage.

Signing out and signing back in:

On your Mac, you can do the following: Open Messages and go to Messages > Preferences. Then go to Accounts and select your iMessage account from the drop-down menu. To exit, click Sign Out. After that, restart your Mac and sign in again.

On your iPad, iPhone, or iPod touch, do the following: Messages > Send & Receive can be found under Settings > Messages. Sign out by entering your Apple ID and clicking Sign Out. After that, restart your device and sign in to your account.

Check to see that your device is connected to the Internet before proceeding (a cellular data or Wi-Fi network).

There is no cellular data on the iPhone.

Problems with the iPhone's Wi-Fi.

Problems with the iPad's Wi-Fi.

Problems with the Wi-Fi on the Mac.

Check to see that your time zone is correctly configured:

mac OS: Select System Preferences from the Apple menu, then Date & Time from the drop-down menu. It's also a good idea to check the box that says "Set date and time automatically."

If you are using iOS or iPad OS, go to Settings > General > Date & Time. Alternatively, you might want to enable the "Set Automatically" option.

Check the Apple System Status page for more information. It's possible that Apple is experiencing iMessage outages.

If you receive the message "Phone Number Is Not Registered With iMessage," refer to this article for more information.

If any of your messages are out of order, please refer to this article.

If you're having trouble sending photos through iMessage, check out this article.

If Messages will not open on your Mac, please see this article.

If macOS Messages freezes or crashes refer to this article for help.

If you receive the "Number Changed to Primary" Notification, please refer to this article.

If you receive the message "Your Carrier May Charge For SMS Messages Used To Activate iMessage," please refer to this article.