Patent ID: 7219229

Claim:
A computer program stored on an information processing device having a memory enabling an electronic mail communication operation over the internet, wherein, the memory having a reference table, a plurality of rows each corresponding to a single electronic mail address, an address column storing an electronic mail address, an enciphering column which includes a key area storing an enciphering key identifier and a software area storing an enciphering software identifier, and a deciphering column which includes a key area storing a deciphering key identifier and a software area storing a deciphering software, the reference table being rewritable in response to a prescribed user operation, the computer program containing instructions which upon execution carries out the following method steps: automatically enciphering a file to be transmitted according to an enciphering key and an enciphering software upon an input of a prescribed enciphering instruction, wherein the specified enciphering key and the enciphering software are specified by looking up the enciphering column of a row of the reference table, the row being specified by using the designated transmission destination electronic mail address as a key, and are read out from the memory of the information processing device by using an enciphering key identifier and an enciphering software identifier, read out from the enciphering column of the reference table, as a key; and automatically deciphering a received enciphered file according to a specified deciphering key and a deciphering software upon an input of a prescribed deciphering instruction, wherein the deciphering key and a deciphering software are specified by looking up the deciphering column of a row of the reference table, the row being specified by using the transmission source electronic mail address as a key, and are read out from the memory of the information processing device by using a deciphering key identifier and a deciphering software identifier, read out from the deciphering column of the reference table, as a key.