Security key input system and method using one-time keypad

A security key input method using a one-time keypad, comprising:

• (A) generating, by an input terminal, the one-time keypad, based on a synchronization between the input terminal and an output terminal;
• (B) converting, by the input terminal, the generated one-time keypad into at least one of a short messaging service (SMS) message or a multimedia messaging service (MMS) message;
• (C) transmitting, by the input terminal, the one-time keypad converted into the at least one of the SMS message or the MMS message to the output terminal;
• (D) outputting, by the output terminal, the received one-time keypad;
• (E) outputting, by the input terminal, a security keypad including one or more null keys each having no identification mark written thereon, and receiving a security key from a user;
• and
• (F) determining, by the input terminal, whether the security key inputted from the user coincides with a preset code, through the one-time keypad, and determining whether the security key is correct or wrong.