two factor and google voice

I’ve been using two factor authentication for a number of years.  I like when services offer a choice of two factor options. Or the common Google Authenticator app. Less of a fan of SMS required two factor. If I lose my phone or number, I can’t two factor authenticate to a few services. The most recent being Venmo. Ironically, Venmo wouldn’t let me change.

One of my friends has used Google Voice for phone for years. I decided to switch to a Google Voice number. This gives me a few advantages:

  • phone rings on multiple devices
  • texts get turned into email which means I can view them on multiple devices (nice for two factor)
  • I’m decoupled from my cell phone number for two factor

Today I’m switching over a bunch of services to use a different phone number for two factor. This table shows the services I can think of where I use two factor.

Interestingly, having possession of the original phone number was not necessary for any of the services. So I could have done this even if I had lost my phone. I had enough other options set up for two factor. Also ironically, I couldn’t switch Venmo which motivated all this. I can close the account though so if this ever becomes a problem…

Service Two Factor Options How Switching Went
Google

(original blog post)

Authenticator, SMS, phone, codes, key, Google prompt Google knew my number in my profile, but I still had to verify to set in profile. And again when wetting as my two factor option. Emailed that changed number.
Amazon

(original blog post)

Authenticator, phone, SMS Under my account added a mobile number. Confirmed with SMS text verification.
Twitter

(original blog post)

Authenticator, SMS, security key, backup code Went to mobile and clicked edit to change number. I didn’t enable SMS, but now it has the right number in case I need it as a one off. Confirmed with SMS text verification.
Facebook Authenticator, SMS, codes, key Went to security and use two factor. Added Google voice and backup. Emailed that added number.

(Only allowed SMS last I looked. Good improvement).

Venmo Just SMS Won’t accept my Google voice number and gave an error that it needs a mobile number. 
GitHub (original blog post) Choice of authenticator, SMS, security keys, recovery tokens (other site), and recovery codes (strings) Clear existing number. Set new Google voice number. Enter code texted to new number. GitHub also emailed me that I added and removed a SMS number.
PayPal

(original blog post)

SMS, phone Confirming my landline number, it had me type a code when they called instead of supplying a code read to me. This seems more secure. Good! The new number was added as unconfirmed. I clicked confirm to get a text to confirm it.
LinkedIn

(original blog post)

SMS I couldn’t find the two factor page without a direct link. I scrolled up and added a phone number. After confirming the verification code, it automatically made the new phone number primary. I couldn’t delete the original since it is used for two factor. So I went to the two factor section and changed the number. it sent me a code again. Then I finally went back and deleted the original number. And for every one of those operations, I had to enter my linked in password. This felt excessive.
DropBox

(original blog post)

Authenticator, SMS, codes, physical device Went to settings and changed my number. I had to enter my authenticator code but not verify possession of the phone number. Emailed that changed two factor settings.
Yahoo

(original blog post)

Email, phone, text Went to account to try to change number. Got an error that it can’t accept a VOIP number. I was able to change it my land line. I use Yahoo almost never so it doesn’t matter whether this is convenient. Emailed that removed and added number.
Slack Authenticator Added my phone number. No verification required.
Apple

(original blog post)

Various Added a trusted phone number and confirmed code. Verified with my computer as well as the code. Removed original number. Emailed that number changed