Patent ID: 6889378

Claim:
A communication method between tasks executed on an operating system, said method comprising: a step for managing the security level of tasks themselves and mutual verification keys for mutual verification between tasks and said operating system, in a table format at said operating system side, wherein said security level has a first level which is secure and a second level which is not secure; a step for reading and writing blocks of tasks of said first level and blocks of tasks of said second level separately into a secure memory block and a non-secure memory block, respectively; a step for providing a first buffer on a first task of a task of said first level, and a second buffer on a second task of a task of said second level, and providing within said operating system memory area for storing data and memory area for storing management information; a step for specifying at said first task an ID and an address appropriated at said first task side, judging at said operating system side which memory block to use based on the security level of said first task and the security level of a first function, and in the event that the security level of said first task and the level for executing said first task are secure, management information is written to said security memory block and data is written as enciphered contents with the ID, address value of management information, and address value of the data body, as a key; and a step for specifying at said second task an ID the same as said second task and an address appropriated at said second task side, judging at said operating system side which secure memory block to use based on the security level of said second task and the security level of a second function, and, in the event that the security level of said second task and the level for executing said second level are secure data, addressed to said second task managed in said secure memory block is searched, and the contents of the buffer where said data exists is copied onto said second task having been deciphered with the ID, address value of management information, and address value of the data body, as a key.