摘要 |
The present invention relates to a device (1) comprising an input for receiving an input; calculation means (P) for producing a response (OUTPUT) in response to the input (INPUT) and a secret key (A) by utilizing a first predetermined function (f), and an output (3) for feeding said response (OUTPUT) further. In order for an attacker not to be able to find out the secret key, the device further comprises a memory (M) in which the key-specific number (RND) is stored, and means for retrieving the key-specific number (RND) from the memory (M) and for feeding it to the calculation means (P') for carrying out predetermined calculation operations (f2) on the basis of the key-specific number (RND) when producing said response (OUTPUT).
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