There was a time (end 2000's?) when multiple popular home wifi router models calculated their default wifi password from their MAC addresses. There where websit

There was a time (end 2000's?) when multiple popular home wifi router models calculated their default wifi password from their MAC addresses. There where websites doing the calculation for you, if you gave them the router's MAC. For me, this was the transitory technology between those laughable free (or sometimes even paid) wifis that where just broken and the time when a) hotels etc. had their wifi finally fixed and b) one could resort to cell phone internet.