According to one embodiment, a storage device includes a nonvolatile memory storing first data, and a device controller which is capable of storing all or a part of the first data stored in the nonvolatile memory as second data to a memory area in a host. The device controller which is configured to calculate a first hash value of the second data stored in the memory area in a first timing, calculate a second hash value of the second data stored in the memory area in a second timing, and detect whether the second data stored in the memory area is tampered between the first and second timings by comparing the second hash value with the first hash value.