Abstract: The purpose of the present invention is to provide a feature which, even when updated data to be written to an ECU is encrypted, is capable of appropriately resuming the writing processing when determined that the writing processing was interrupted while in progress. An electronic control device according to the present invention, wherein a first data block included in the updated data is encrypted by using a second data block, and when the writing processing for writing the first data block to the storage unit is interrupted while in progress, updated data which includes both the first data block and the second data block is reacquired, after which the first data block is decoded again by using the reacquired second data block.

Abstract: The purpose of the present invention is to provide technology whereby a retransmission start address can be properly identified even when update data is compressed or encrypted. In the electronic control device according to the present invention, update data includes at least one of compressed data and encrypted data and includes unprocessed data that is neither compressed nor encrypted, and the unprocessed data retains an address list that can identify the positions of data blocks included in the update data.

Abstract: Provided is a technique for enabling software having different memory maps to be written in a nonvolatile memory of an electronic control device in reprogramming of control software. The electronic control device includes a microcomputer including a CPU and a nonvolatile memory. The nonvolatile memory includes activation software, control software, and validity confirmation information for confirming validity of the control software. A storage area of the validity confirmation information in the nonvolatile memory is different from a storage area of the activation software.

Abstract: When a control program is updated by a device that can select and execute one of two control programs, an amount of data to be transferred is reduced to shorten time required for update of a program. A first rewritable storage unit that stores two programs, a CPU that selects and executes one of the two programs, and a second rewritable storage unit that stores common data accompanying the two programs are included.