When users log in to banking systems from unfamiliar devices, banks often send them a text message or email containing a $6$ digit verification code. These verificatiWhen users log in to banking systems from unfamiliar devices, banks often send them a text message or email containing a $6$ digit verification code. These verification codes typically only use the chosen from $0,1,2,3,4,5,6,7,8,90,1,2,3,4,5,6,7,8,9.$on codes typically only use the chosen from $0,1,2,3,4,5,6,7,8,90,1,2,3,4,5,6,7,8,9.$