You don't have to mass update a set of records. What I did was create a formula and use the same SHA256() formula used to create the secure links, but in a Formula - Text with some common value or random generated string so it would be the same across all records. Then create an ask the user report and get the URL pointed to that with the "key" already filled out. That said, I don't feel like this is a great solution.
Another option is maybe to create a table or new form and display a report, the report should display records if the secure link is read by the form as it normally would be. Also not the ideal solution, but one option to consider.