Signal uses your existing phone number so there are no separate logins or usernames to manage or lose. Your phone number can be your
- Mobile device number
- Google Voice number
- Any VoIP number
- Landline number
- All Signal messaging and calling that you send or receive will display the number you registered Signal iOS with.
See also the support page on verification for iOS.
- If you send a Signal message, it is private and originates from your Signal registered number. Your recipient will see your Signal registered number.
- If you send an insecure SMS/MMS, it originates from you mobile SIM card phone number as it is going through your mobile plan and will reveal your mobile number to your recipient.
- If you enable Google Voice SMS forwarding, then you can respond to insecure SMS/MMS messages linked to your Google Voice number, it will go through your mobile plan and Google and it will show your Google Voice number to your recipient.
- If you place a Signal call, it is private and originates from your Signal registered number and is going through the internet.
- If you place an insecure call, it originates from you mobile SIM card phone number and goes through your mobile plan.
See also the support page on verification for Android.