Bill, SMS for 2FA is not fine. I recommend you study the issue in more depth. It’s not just me who disagrees with you: https://www.schneier.com/blog/archives/2016/08/nist_is_no_long.html -mel On Apr 18, 2021, at 6:31 AM, William Herrin <bill@herrin.us> wrote: On Sat, Apr 17, 2021 at 6:00 PM Eric Kuhnke <eric.kuhnke@gmail.com> wrote: Anecdotal: With the prior consent of the DID holders, I have successfully ported peoples' numbers using nothing more than a JPG scan of a signature that looks like an illegible 150 dpi black and white blob, pasted in an image editor on top of a generic looking 'phone bill'. Hi Eric, SMS for 2FA is fine. It's understood that a single authentication factor is not secure enough; that's why you use two. SMS for 1FA is hugely risky and should not be used for anything important, like money. SMS for a password reset is an example of 1FA -- your ability to receive SMS messages at the required phone number becomes the sole authentication factor needed to access the account. If the adversary has captured your password -and- reprogrammed your phone number, what makes you think they lack the wherewithal to have captured the shared secret used to generate your TOTP code? Regards, Bill Herrin -- William Herrin bill@herrin.us https://bill.herrin.us/