AT&T, Comcast Announce Verification Milestone To Help Fight Robocalls (usatoday.com)

"The fight against robocalls can even bring telecom rivals together," reports USA Today: AT&T and Comcast said Wednesday that they can authenticate calls made between the two different phone providers' networks, a potential industry first and the latest in the long-running battle against spam calls... The system, which uses a method developed in recent years, verifies that a legitimate call is being made instead of one that has been spoofed by spammers, scammers or robocallers with a "digital signature." The recipient network then confirms the signature on its side. The companies said consumers will get a notification that a call is verified, but exactly what that will look like is not yet known.

Both AT&T and Comcast will roll out the system to home phone users later this year at no extra charge. AT&T also said it will introduce the feature to its mobile users this year... Other major wireless and traditional home voice providers have pledged support for the verification method, including Verizon, T-Mobile, Sprint, Charter, Cox and Vonage, with several announcing plans to roll out or test the feature in 2019.
The day Comcast and AT&T made their announcement, AT&T's CEO was giving a live interview that was interrupted by a robocall.

Comments

Also don't forget the logic error

[raymorris]

Btw before even trying to figure out a technical protocol, don't forget you need to fix the logic. A station is not a DID and a DID is not a station. It *may* be that your station (phone) has a phone number, only one phone number, and you never use call forwarding, and no other phone uses that number. Those things might be true for you today, but those are absolutely not rules in the phone system. Some people DO have call forwarding, and a a lot more.

It's a lot like the name Google.com - that does NOT identify a particular server. A dialed number doesn't identify a particular phone any more than Google.com identifies a particular computer. There are many buildings full of servers, and any request for Google.com will use several randomly selected servers from among thousands.

For example, I volunteer to receive calls for a crisis hotline which gets a few calls per month. The person in need of help calls the crisis number. They know which service they are trying to reach. They have no idea which phones will ring, and they don't care. They are asking for a service (1-800-help), not for a specific device (an IMEI or other station ID).

I'm not always able to answer the phone of course, so the crisis line doesn't just forward the call to my mobile phone. It rings my phone, and while it's ringing my phone if I don't answer within 10 seconds it starts also ringing another volunteer, ten seconds later it adds a third, etc, until someone both answers and presses 1 to accept the call.

Now suppose my phone were to call the person back, asking "did you call Ray's phone?" Their phone has no idea whether they called my phone or not! They called 1-800-help, not "Ray's LG phone, the one he just bought". Their phone has no way of answering that question.

The number you dial doesn't identify a device. "Did you call Ray's mobile" isn't an answerable question.

Similarly, if I miss a call that rings my mobile, I don't know if the caller was calling the crisis line, my business number, or my personal number. Any of those three numbers, identifying three different services, might ring the same device.

So get it out of your head that there is some fixed relationship between a phone and a number that someone can call. There isn't.