Data security system for transmitting and receiving data between a memory card and a computer using a public key cryptosystem

摘要

In a system wherein a memory card is connected to a computer, data stored in a memory device in the memory card is read by a processor provided in the computer. An address signal and a data signal from the computer to the memory card, and/or a data signal from the memory card to the computer are coded with coding keys by a coder, while the coded signal is decoded by a decoder with a decoding key corresponding to the coding keys. The coder and the decoder adopts a public key system, and it is difficult to determine the decoding key even if the coding keys are known. In modified examples, coding keys are not provided beforehand in the computer or memory card, and they are latched in a latch device when the memory card is connected to the computer. When the coding keys and decoding keys are stored in the memory card, they are changed for each memory card.