Patent ID: 9311256
Filing Date: 2016-04-12
CPC Classification: G06F,H04L

Claim Text:
1. A storage device comprising: a cipher processor that receives data from a host and encrypts the data received from the host using a first cryptographic key; a first non-volatile memory that stores the data encrypted by the cipher processor; and a key processor that replaces a first cryptographic key having been used by the cipher processor with a cryptographic key that is different from the first cryptographic key according to a request from the host, wherein the key processor comprises: a key generator that generates a second cryptographic key; a history manager that converts the first cryptographic key and past cryptographic keys previously used to encrypt received data into first information by an operation and stores the first information, said operation having a property of converting the same two input values into the same output values respectively and two different input values into output values different from each other; a converter processor that converts the second cryptographic key into second information by the same operation used to convert the first cryptographic key and the past cryptographic keys into said first information; and a comparator that reads out the first information from the history manager, compares the read-out first information and the second information, and when the read-out first information and the second information have different values, replaces the first cryptographic key with the second cryptographic key and when the read-out first information and the second information have the same values, discards the second cryptographic key and generates a new second cryptographic key, wherein the first non-volatile memory comprises a plurality of storage areas, wherein the cipher processor uses a different cryptographic key for each of the plurality of storage areas, and wherein the request specifies one of the plurality of storage areas.