Method for replacing contents of a data storage unit

1. A data storage device, comprising:

a plurality of data storage units;

a physical random number generator with a noise source based on a physical noise process, implemented to generate physical random numbers;

a pseudo random number generator implemented to generate pseudo random numbers;

a combiner implemented to combine the physical random numbers and the pseudo random numbers; and

a replacer implemented to select one of the data storage units, in which data is to be stored, depending on a sequence of driving signals,

wherein the combiner is implemented to feed, when there is a new physical random number, the new physical random number into the pseudo random number generator as a seed for re-initializing, and

wherein the combiner is implemented to generate the sequence of driving signals using one of the pseudo random numbers, which has been generated by the pseudo random number generator based on the new physical random number as a seed; and

a mode controller implemented to access the combiner or the replacer via a mode line so as to switch, within a predetermined time interval, from a random non-deterministic replacement strategy used in selecting a data storage unit, which is based on the physical random numbers from the physical random number generator to a deterministic replacement strategy used in selecting a data storage unit, which is either solely based on the pseudo random numbers or is an alternative deterministic replacement strategy,

wherein the mode controller is implemented to bring about the deterministic replacement strategy when calculations in program sections which are less relevant in terms of security are to be performed in a processor coupled to the data storage device or when guaranteed or predictable run times are required for calculations in program sections by the processor, and to bring about the random non-deterministic replacement strategy when calculations in program sections which are more relevant in terms of security are to be performed in the processor coupled to the data storage device.

2. The data storage device as claimed in claim 1 , wherein the noise source of the physical random number generator comprises a shot-noise source or a source for thermal noise.

3. The data storage device as claimed in claim 1 , wherein the replacer is implemented to select a sequence of addresses, and

wherein the combiner is implemented to create driving signals for the sequence of addresses, such that one of the driving signals depends on the physical random number and a different one of the driving signals depends on the pseudo random number.

4. The data storage device as claimed in claim 1 ,

wherein the mode controller is implemented to bring about a switching of the replacement strategy at regular or random intervals.

5. The data storage device as claimed in claim 4 , wherein a random time interval is determinable by the mode controller depending on the physical random number of the physical random number generator.

6. The data storage device as claimed in claim 1 , which is implemented as an associative cache memory.

7. A method for replacing contents of a data storage device comprising a plurality of data storage units, the method comprising:

providing physical random numbers dependent on a physical noise process using a physical random number generator;

generating pseudo random numbers with a pseudo random number generator;

using the physical random numbers and the pseudo random numbers to generate a sequence of driving signals for a selection of a data storage unit depending on the physical random numbers and the pseudo random numbers;

selecting a data storage unit from the plurality of data storage units in dependence on the physical random numbers, depending on the sequence of driving signals; and

storing data to be stored in the selected data storage unit,

wherein, in using the physical random numbers and the pseudo random numbers, when there is a new physical random number, the new physical random number is fed into the pseudo random number generator as a seed for re-initializing,

wherein, in generating the sequence of driving signals, one of the pseudo random numbers generated by the pseudo random number generator based on the new physical random number as a seed is used,

wherein a mode controller switches, within a predetermined time interval, from a random non-deterministic replacement strategy used in selecting a data storage unit, which is based on the physical random numbers from the physical random number generator to a deterministic replacement strategy used in selecting a data storage unit, which is either solely based on the pseudo random numbers or is an alternative deterministic replacement strategy, and

wherein the mode controller is implemented to bring about the deterministic replacement strategy when calculations in program sections which are less-relevant in terms of security are to be performed in the processor coupled to the data storage device or when non-guaranteed or non-predictable run times are allowable for calculations in program sections by the processor, and to bring about the random non-deterministic replacement strategy when calculations in program sections which are more relevant in terms of security are to be performed in the processor coupled to the data storage device.

8. The data storage device as claimed in claim 1 , wherein the deterministic replacement strategy comprises a least-recently used replacement strategy, a round robin replacement strategy or a replacement strategy being solely based on pseudo random numbers and not being based on physical random numbers.