The security solution was probably that the user had to type the account's PIN, and that it uses the phone line instead of the Internet. It's from 1995 (check the date of the Folha de São Paulo article above), not using encryption at all was very common back then; and even today, phone lines are still considered reliable enough that one can type the account PIN on it without any encryption (for instance: if I want to solve any issue with my credit card through the phone, I must type the full number on the card and the credit card PIN before the URA will connect me to an operator).
