Signal has just said that it is phasing out support for SMS and MMS on the Android client of the instant messaging app in order to simplify the user experience and prioritize security and privacy. For those who don’t know about this feature, you may be surprised to see this announcement. But in fact, Signal for Android, which uses the Axolotl Ratchet protocol (started with TextSecure), can also be configured as the default SMS / MMS application.
In a blog post, the officials explained, “We understand that SMS support no longer makes sense. So in an effort to achieve a cleaner experience, Signal has begun phasing out SMS support for Android clients.
Existing Signal for Android customers will have a few months to complete the transition, during which time SMS messages can be exported to another app and contacts will be made aware that they can switch to the Signal platform for discussion (if they don’t want to change to another channel).
In addition, this change will only affect Android users who have Signal as their default SMS app, which will display both Signal/SMS contacts (marked in blue letters) when the app is used as the unified Android messaging app.
The main reason for this is that Signal considers text-only SMS messages to be insecure. In addition to the possibility of being intercepted in various ways (such as pseudo base stations), it also allows global mobile operators to access the metadata of the message.
On the other hand, displaying encrypted/unencrypted messages in the same interface can easily lead to confusion for users – even if Signal has added similar markers.
What’s more, only mobile operators in the US and Europe are currently pushing affordable/unlimited SMS packages, while rates in the southern hemisphere are generally unaffordable.
A third reason is that, given the high cost of SMS in some regions, users are likely to overpay their bills when they send SMS messages instead of Signal messages by mistake.
In summary, Signal did not make this decision lightly, but felt it was necessary to ensure that Signal met the highest privacy standards going forward.