Multi-factor entropy sourcing for random number generators

1. A method, comprising:

identifying, by a processing device, a plurality of entropy sources;

receiving random bits from each of the plurality of entropy sources;

identifying a minimum number of bits among numbers of bits received from each of two or more entropy sources of the plurality of entropy sources;

mixing, into an entropy pool, at least the identified minimum number of bits received from each entropy source of two or more entropy sources; and

increasing a size of the entropy pool by the identified minimum number of bits.

2. The method of claim 1 , wherein an entropy source of the plurality of entropy sources is provided by a hardware device represented by one of: a keyboard, a disk controller, a mouse, a processor, or a network interface controller (NIC).

3. The method of claim 1 , wherein the entropy pool is represented by a memory buffer that is protected from being accessed by user-level processes.

4. The method of claim 1 , wherein receiving the random bits comprises one of: measuring timing of events associated with the entropy sources or counting events associated with the entropy sources.

5. The method of claim 1 , wherein receiving the random bits comprises compressing the random bits.

6. The method of claim 1 , further comprising:

calculating a digest of at least the identified minimum number of bits received from each entropy source using at least one of: a cyclic redundancy check (CRC) function or a cryptographic hash function.

7. The method of claim 1 , wherein mixing at least the identified minimum number of bits into the entropy pool is performed by an interrupt handler routine.

8. The method of claim 1 , further comprising:

responsive to receiving a request for a random number, retrieving a certain number of bits from the entropy pool; and

reducing the size of the entropy pool by the certain number of bits.

9. The method of claim 8 , wherein retrieving the certain number of bits from the entropy pool comprises blocking a caller process responsive to determining that a number of bits available in the entropy pool is less than a number of bits that is needed to produce a return value.

10. The method of claim 8 , further comprising:

returning, to a calling process, a random value represented by a digest of the certain number of bits retrieved from the entropy pool.

11. A system, comprising:

a memory; and

a processing device operatively coupled to the memory, the processing device to:

receive random bits from each of a plurality of entropy sources;

identify a minimum number of bits among numbers of bits received from each of two or more entropy sources of the plurality of entropy sources;

mix, into an entropy pool, at least the identified minimum number of bits received from each entropy source of two or more entropy sources; and

increase a size of the entropy pool by the identified minimum number of bits.

12. The system of claim 11 , wherein an entropy source of the plurality of entropy sources is provided by a hardware device represented by one of: a keyboard, a disk controller, a mouse, a processor, or a network interface controller (NIC).

13. The system of claim 1 , wherein the entropy pool is represented by a memory buffer that is protected from being accessed by user-level processes.

14. The system of claim 11 , wherein the processing device is further to:

calculate a digest of at least the identified minimum number of bits received from each entropy source using at least one of: a cyclic redundancy check (CRC) function or a cryptographic hash function.

15. The system of claim 1 , wherein the processing device is further to:

responsive to receiving a request for a random number, retrieve a certain number of bits from the entropy pool; and

reduce the size of the entropy pool by the certain number of bits.

16. A computer-readable non-transitory storage medium comprising executable instructions to cause a processing device to:

identify, by the processing device, a plurality of entropy sources;

receive random bits from each of the plurality of entropy sources;

identify a minimum number of bits among numbers of bits received from each of two or more entropy sources of the plurality of entropy sources;

mix, into an entropy pool, at least the identified minimum number of bits received from each entropy source of two or more entropy sources; and

increase a size of the entropy pool by the identified minimum number of bits.

17. The computer-readable non-transitory storage medium of claim 16 , further comprising executable instructions to cause the processing device to:

calculate a digest of at least the identified minimum number of bits received from each entropy source using at least one of: a cyclic redundancy check (CRC) function or a cryptographic hash function.

18. The computer-readable non-transitory storage medium of claim 16 , further comprising executable instructions to cause the processing device to:

responsive to receiving a request for a random number, retrieve a certain number of bits from the entropy pool; and

reduce the size of the entropy pool by the certain number of bits.

19. The computer-readable non-transitory storage medium of claim 18 , wherein instructions to retrieve the certain number of bits from the entropy pool comprise executable instructions to cause the processing device to:

block a caller process responsive to determining that a number of bits available in the entropy pool is less than a number of bits that is needed to produce a return value.

20. The computer-readable non-transitory storage medium of claim 18 , further comprising executable instructions to cause the processing device to:

return, to a calling process, a random value represented by a digest of the certain number of bits retrieved from the entropy pool.