Patent ID: 8077867

Claim:
A confidential information processing device which performs a plurality of cryptographic computations on different target data included in a data stream inputted from an external device, said confidential information processing device comprising: at least one stream analyzer operable to determine the target data by analyzing the data stream; at least one cryptographic computer operable to hold a context including at least one of a key used for the cryptographic computation, an initial value, and intermediate information during cryptographic computation, and perform the cryptographic computation using the context that is being held; a context storage operable to store a plurality of the contexts; a correspondence table storage operable to store a correspondence table which indicates the number of cryptographic computations to be performed for the data stream and a context to be used for each of the cryptographic computations; a context controller operable to, when the context held in said cryptographic computer does not match the context to be used indicated in the correspondence table, save the context held in said cryptographic computer to the context storage and restore the context to be used for the cryptographic computation indicated in the correspondence table out of the plurality of contexts stored in said context storage to said cryptographic computer; and a stream controller operable to output the data stream on which the cryptographic computation is performed by said cryptographic computer to the external device, when the number of the cryptographic computations matches the number indicated in the correspondence table, and to output the data stream on which the cryptographic computation is performed by said cryptographic computer to said stream analyzer, when the number of the cryptographic computation does not match the number of cryptographic computations indicated in the correspondence table.