Nathan, thanks for your comments. They make a lot of sense.
I spoke with Charles Schwab on another matter, and they added a little more detail. The way I understood it, there are several layers of connectivity in something called secure socket links. These SSL interact with various identifiers within Schwab to make sure my computer is what it says it is, and there are no known eavesdroppers, etc. SSL 128 is the current standard, they told me.
When MS comes out with a new version of software, like Win 7 to Win 10, they build bridges within the 10 to link back to code written by me or a vendor for a 7 product and make it work. But many newer features in the 10 may not work as intended. If I'm working on an SSL version 1994 that may create difficulties.
Apparently, there are various ways for Schwab to authenticate my computer. They will be going to a two factor authentication soon. That means I enter my user name, click enter and it is passed to Schwab. Schwab passes back some code, and my machine is prompted for my password. That goes back in a different pass to Schwab, after a massage with the info just received.
The feds have apparently imposed regs on banks, brokers etc which require them to maintain more secure connections. That's why Win XP, Win Vista, etc connections aren't supported by some security systems.
(Of course, the NSA, with its billions of dollars in investment, still gets hacked by guys working out of a cave somewhere. NOT POLITICAL!)
Dreams come in all sizes, shapes, and colors.