Just have one vote tied to each SSN, that you have to verify using an online authenticator.
In Sweden, we have BankID, which has become the de-facto way to sign and agree to terms online. You can only request a BankID from your online bank, it's tied to your SSN and device (an app you can install on iOS and Android), and for every device you want to add it to, for example if you want to add your BankID to a new phone, you have to go to the online banking website and verify it. I have a small banking authenticator that's tied to my bank account that I have to use whenever I approve adding BankID to any new device, so there are several layers to verify it's you.
1. You can only get the banking device from your bank if you go there and confirm your bank account with your ID. Tied to the device, is a PIN code you select.
2. You can only order a BankID to your device by logging in on your online bank, with the help of the banking device you got.
3. When confirming the order, you have to use the banking device and your PIN to confirm it.
4. Once the BankID has been installed and verified, you need to select a different 6 digit PIN code that you use whenever you confirm anything.
You can also get a separate BankID on "card" that's a small electronic device you use to verify terms whenever it registers you using your SSN for any service.
I file my taxes with this. I just open the IRS's bank, check if their estimate is correct (it always is since I don't have to manually report anything separately), I click on agree, enter my SSN, my BankID app opens, I enter my PIN code and verify that the estimate is correct, click on agree, and done!
The same system could be used for online voting, with less risks for fraud than when voting in person.
In Sweden, we have BankID, which has become the de-facto way to sign and agree to terms online. You can only request a BankID from your online bank, it's tied to your SSN and device (an app you can install on iOS and Android), and for every device you want to add it to, for example if you want to add your BankID to a new phone, you have to go to the online banking website and verify it. I have a small banking authenticator that's tied to my bank account that I have to use whenever I approve adding BankID to any new device, so there are several layers to verify it's you.
1. You can only get the banking device from your bank if you go there and confirm your bank account with your ID. Tied to the device, is a PIN code you select.
2. You can only order a BankID to your device by logging in on your online bank, with the help of the banking device you got.
3. When confirming the order, you have to use the banking device and your PIN to confirm it.
4. Once the BankID has been installed and verified, you need to select a different 6 digit PIN code that you use whenever you confirm anything.
You can also get a separate BankID on "card" that's a small electronic device you use to verify terms whenever it registers you using your SSN for any service.
I file my taxes with this. I just open the IRS's bank, check if their estimate is correct (it always is since I don't have to manually report anything separately), I click on agree, enter my SSN, my BankID app opens, I enter my PIN code and verify that the estimate is correct, click on agree, and done!
The same system could be used for online voting, with less risks for fraud than when voting in person.