Android 版 Signal が SMS 対応を取りやめる話

The most important reason for us to remove SMS support from Android is that plaintext SMS messages are inherently insecure. They leak sensitive metadata and place your data in the hands of telecommunications companies. With privacy and security at the heart of what we do, letting a deeply insecure messaging protocol have a place in the Signal interface is inconsistent with our values and with what people expect when they open Signal.

Back when we started supporting plaintext SMS messaging things were different. Data plans were much more expensive generally, and were totally inaccessible in many parts of the world. Now, data plans are cheaper and far more ubiquitous than they were nearly a decade ago. In a reversal, the cost of sending SMS is now prohibitively high in many parts of the world. This brings us to our second reason: we’ve heard repeatedly from people who’ve been hit with high messaging fees after assuming that the SMS messages they were sending were Signal messages, only to find out that they were using SMS, and being charged by their telecom provider. This is a terrible experience with real consequences.

Third, there are serious UX and design implications to inviting SMS messages to live beside Signal messages in the Signal interface. It’s important that people don’t mistake SMS messages sent or received via the Signal interface as secure and private when in fact they are not. And while we flag the difference between them in the app, we can only do so much on the design side to prevent such misunderstandings.

After much discussion, we determined that we can no longer continue to invest in accommodating SMS in the Android app while also dedicating the resources we need to make Signal the best messenger out there.

特に、最古の携帯電話ネットワークの2G通信では、通話やテキストメッセージは簡単に傍受されてしまう。そのため、我々はAppleとGoogleに対し、ユーザが（訳注：AndroidやiOSで）2Gをオフにできる機能を提供するよう要請してきた。Googleは最新の端末にこのオプションを導入したが、ロシアとウクライナではほぼ利用できない。またAppleは未だに対応していない。

我々は可能な限り2Gの利用をやめるよう促してきたが、3G、4G、5Gだからセキュアだというわけではない。とりわけ、音声とテキスト通信にとってはセキュアなオプションとは言えない。これらのネットワークでは、通信がエンドツーエンドで暗号化されていないため、通信事業者を含め、通信の傍受者が通信内容を見聞きできてしまう。

あなたがどこに住んでいようと、特にロシアとウクライナにおいては、政府当局からあなたの通信のプライバシーを守るために、電話やSMSに依存してはならない。

2要素認証（2FA：アカウントにログインする際に取得するコード）については、できる限りSMSではなくアプリを使用することを推奨する。