Method and apparatus of retaining maximum speed of flip-flop metastability based random number generators
First Claim
1. An apparatus for retaining maximum speed of a flip-flop metastability based random number generator, comprising:
- a fixed delay unit having an input for receiving a common signal from a digital signal generator, said fixed delay unit providing a fixed period of delay to the signal as an output;
a variable delay unit having an input for receiving the common signal from the digital signal generator, said variable delay unit being tunable to provide a variable delay to the common signal as an output;
a pair of NAND gates each of which has a first input that receives a respective output of one of fixed delay unit and variable delay unit;
an output of a first NAND gate is input to a second NAND gate of the pair of NAND gates, and an output of the second NAND gate is input to the first NAND gate of the pair of gates;
a frequency measurement and delay tuning module that receives an output of a first NAND gate of the pair of NAND Gates, said module checks the frequency of random number bit generation and updates variable delay unit to according to predetermined criteria to tune the variable delay unit so as to maximize the speed of the random bit generation.
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Abstract
An apparatus, system and method for retaining the maximum speed of flip-flop metastability based random number generators includes a fixed delay unit having an input for receiving a common signal from a digital signal generator, and a variable delay unit having an input also for receiving the common signal from the digital signal generator. Each of the delay units is attached to the input of a respective logic gate. A frequency measurement of the occurrences of metastability, which is the speed of the random bit generation and delay tuning module 312 receives an output of one of the first NAND gates, checks the frequency of random number bit generation and updates the variable delay unit to according to predetermined criteria to tune the delay so as to maximize the speed of the random bit generation. An algorithm is used to determine whether the optimum delay is equal to, smaller or larger than the delay used to achieve the measured frequency.
11 Citations
19 Claims
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1. An apparatus for retaining maximum speed of a flip-flop metastability based random number generator, comprising:
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a fixed delay unit having an input for receiving a common signal from a digital signal generator, said fixed delay unit providing a fixed period of delay to the signal as an output;
a variable delay unit having an input for receiving the common signal from the digital signal generator, said variable delay unit being tunable to provide a variable delay to the common signal as an output;
a pair of NAND gates each of which has a first input that receives a respective output of one of fixed delay unit and variable delay unit;
an output of a first NAND gate is input to a second NAND gate of the pair of NAND gates, and an output of the second NAND gate is input to the first NAND gate of the pair of gates;
a frequency measurement and delay tuning module that receives an output of a first NAND gate of the pair of NAND Gates, said module checks the frequency of random number bit generation and updates variable delay unit to according to predetermined criteria to tune the variable delay unit so as to maximize the speed of the random bit generation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A computer readable medium comprising the following algorithm of executable instructions for generating random numbers:
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(i) setting a queue length at a predetermined value;
(ii) setting a predetermined number of delay values;
(iii) designating a standard deviation (dmax) of steps;
(iv) starting with speed of 0;
(v) starting with a median delay;
(vi) setting an insertion point in the queue while keeping an infinite loop at maximum speed;
(vii) designating a number of steps of normal distribution;
(viii) ensuring that |step|>
0;
(ix) obtaining a last maximum speed and its index in the queue;
(x) setting the delay as imax;
(xi) repeating for next next delay value (from 1 to
256);
(xii) setting delay (dly) and getting speed (spd);
(xiii) storing trial results of speed and updating a variable delay unit used for random number generation;
(xiv) moving/increasing insertion point i in the queue by 1;
(xv) if the insertion point i>
que length, and i=1, then ending the routine;
(xvi) go to step (xi).
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11. A system for retaining maximum speed of flip-flop metastability based random number generation comprising:
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means to receive a common signal from an output of at least one flip-flip;
a fixed delay unit having an input for receiving the common signal from the flip-flop, said fixed delay unit delaying the output of the signal by a fixed period before being output;
a variable delay unit having an input for receiving the common signal from the flip-flop, said variable delay unit being tunable to provide a variable delay to the common signal as an output;
a pair of NAND gates, each of which has a first input that receives a respective output of one of fixed delay unit and variable delay unit;
an output of a first NAND gate is input to a second NAND gate of the pair of NAND gates, and an output of the second NAND gate is input to the first NAND gate of the pair of gates;
a frequency measurement and delay tuning module that receives an output of a first NAND gate of the pair of NAND Gates, said module checks the frequency of random number bit generation and updates variable delay unit to according to predetermined criteria to tune the delay so as to maximize the speed of the random bit generation. - View Dependent Claims (12, 13, 14)
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15. A method for retaining the maximum speed of a flip-flop metastability based random number generator comprising the following steps:
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(a) measuring the frequency of random bit generation;
(b) determining whether a predetermined period of time has passed since a previous adjustment of a variable delay unit;
(c) if the predetermined period in step (b) has passed, determining whether the frequency measured in step (a) is at a maximum;
(d) if it has been determined in step (c) that the frequency is at a maximum, reverting to step (a), otherwise, adjusting the variable unit by a predetermined amount according to an algorithm that determines whether the variable delay should be larger, equal to, or smaller than optimum frequency by a predetermined amount based on the frequency measured in step (a);
(e) resetting a timer that measures a predetermined period of time between adjustments of the variable unit, and returning to step (a). - View Dependent Claims (16, 17, 18, 19)
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Specification