Application of secret sharing schemes at multiple levels of a dispersed storage network

1. A method comprises:

dispersed storage error encoding, by a computing device of a dispersed storage network (DSN), a data segment of a data file to produce a set of encoded data shares, wherein the dispersed storage error encoding uses a first threshold based secret sharing scheme in accordance with first secret sharing parameters;

selecting, by the computing device, a set of storage units of the DSN for storing the set of encoded data shares;

sending, by the computing device, the set of encoded data shares to the set of storage units;

receiving, by a first storage unit of the set of storage units, a first encoded data share of the set of encoded data shares;

encoding, by the first storage unit, the first encoded data share using a second threshold based secret sharing scheme in accordance with second secret sharing parameters to produce a first set of encoded data sub-shares, wherein the first secret sharing parameters differ from the second secret sharing parameters; and

storing, by the first storage unit, the first set of encoded data sub-shares in a set of memory devices of the first storage unit, wherein a threshold number of encoded data sub-shares of the first set of encoded data sub-shares is decodable to recover the first encoded data share.

2. The method of claim 1 further comprises:

receiving, by the first storage unit, a read request for the first encoded data share from a requesting device;

rebuilding, by the first storage unit, the first encoded data share from at least the threshold number of encoded data sub-shares of the first set of encoded data sub-shares; and

sending, by the first storage unit, the rebuilt first encoded data share to the requesting device.

3. The method of claim 1 further comprises:

receiving, by a second storage unit of the set of storage units, a second encoded data share of the set of encoded data shares;

encoding, by the second storage unit, the second encoded data share using a third threshold based secret sharing scheme in accordance with third secret sharing parameters to produce a second set of encoded data sub-shares; and

storing, by the second storage unit, the second set of encoded data sub-shares in a set of memory devices of the second storage unit, wherein a threshold number of encoded data sub-shares of the second set of encoded data sub-shares is decodable to recover the second encoded data share.

4. The method of claim 3 , wherein the threshold number of encoded data sub-shares of the first set of encoded data sub-shares differs from the threshold number of encoded data sub-shares of the second set of encoded data sub-shares.

5. The method of claim 1 , wherein the first threshold based secret sharing scheme and the second threshold based secret sharing scheme utilize a common threshold based secret sharing function.

6. The method of claim 1 , wherein the first threshold based secret sharing scheme and the second threshold based secret sharing scheme utilize differing threshold based secret sharing functions.

7. The method of claim 1 further comprises:

determining the first secret sharing parameters based on one or more of a number of storage units of the set of storage units, a sub-sharing capability of one or more storage units of the set of storage units, or a reliability level of one or more storage units of the set of storage units.

8. The method of claim 1 further comprises:

determining the second secret sharing parameters based on one or more of a number of memory devices of the first storage unit, a reliability level of memory devices of the first storage unit, an available capacity level of the memory devices of memory devices of the first storage unit, or random selection.

9. The method of claim 1 , wherein the first threshold based secret sharing scheme is an all-or-nothing transform with Reed Solomon coding (AONT-RS) secret sharing scheme.

10. The method of claim 1 , wherein the first threshold based secret sharing scheme and the second threshold based secret sharing scheme are differing schemes from the group including an all-or-nothing transform with Reed Solomon coding (AONT-RS) secret sharing function, a Shamir secret sharing function, a Blakley secret sharing function, and a Rabin information dispersal algorithm (IDA) secret sharing function.

11. A computer readable storage device comprises:

a first storage section that stores operational instructions that, when executed by a computing device of a dispersed storage network (DSN), causes the computing device to:

dispersed storage error encode, using a first threshold based secret sharing scheme in accordance with first secret sharing parameters, a data segment of a data file to produce a set of encoded data shares;

select a set of storage units of the DSN for storing the set of encoded data shares; and

send the set of encoded data shares to the set of storage units; and

a second storage section that stores operational instructions that, when executed by a first storage unit of the set of storage units, causes the first storage unit to:

receive a first encoded data share of the set of encoded data shares;

encode the first encoded data share using a second threshold based secret sharing scheme in accordance with second secret sharing parameters to produce a first set of encoded data sub-shares, wherein the first secret sharing parameters differ from the second secret sharing parameters; and

store the first set of encoded data sub-shares in a set of memory devices of the first storage unit, wherein a threshold number of encoded data sub-shares of the first set of encoded data sub-shares is decodable to recover the first encoded data share.

12. The computer readable storage device of claim 11 further comprises:

a third storage section further stores operational instructions that, when executed by the first storage unit, causes the first storage unit to:

receive a read request for the first encoded data share from a requesting device;

rebuild the first encoded data share from at least the threshold number of encoded data sub-shares of the first set of encoded data sub-shares; and

send the rebuilt first encoded data share to the requesting device.

13. The computer readable storage device of claim 11 further comprises:

a third storage section further stores operational instructions that, when executed by a second storage unit of the set of storage units, causes the second storage unit to:

receive a second encoded data share of the set of encoded data shares;

encode the second encoded data share using a third threshold based secret sharing scheme in accordance with third secret sharing parameters to produce a second set of encoded data sub-shares; and

store the second set of encoded data sub-shares in a set of memory devices of the second storage unit, wherein a threshold number of encoded data sub-shares of the second set of encoded data sub-shares is decodable to recover the second encoded data share.

14. The computer readable storage device of claim 13 , wherein the threshold number of encoded data sub-shares of the first set of encoded data sub-shares differs from the threshold number of encoded data sub-shares of the second set of encoded data sub-shares.

15. The computer readable storage device of claim 11 , wherein the first threshold based secret sharing scheme and the second threshold based secret sharing scheme utilize a common threshold based secret sharing function.

16. The computer readable storage device of claim 11 , wherein the first threshold based secret sharing scheme and the second threshold based secret sharing scheme utilize differing threshold based secret sharing functions.

17. The computer readable storage device of claim 11 , where the first storage section further stores operational instructions that, when executed by the computing device, cause the computing device to:

determine the first secret sharing parameters based on one or more of a number of storage units of the set of storage units, a sub-sharing capability of one or more storage units of the set of storage units, or a reliability level of one or more storage units of the set of storage units.

18. The computer readable storage device of claim 11 , where the second storage section further stores operational instructions that, when executed by the first storage unit, causes the first storage to:

determine the second secret sharing parameters based on one or more of a number of memory devices of the first storage unit, a reliability level of memory devices of the first storage unit, an available capacity level of memory devices of the memory devices of the first storage unit, or random selection.

19. The computer readable storage device of claim 11 , wherein the first threshold based secret sharing scheme is an all-or-nothing transform with Reed Solomon coding (AONT-RS) secret sharing scheme.

20. The computer readable storage device of claim 11 , wherein the first threshold based secret sharing scheme and the second threshold based secret sharing scheme are differing schemes from the group including an all-or-nothing transform with Reed Solomon coding (AONT-RS) secret sharing function, a Shamir secret sharing function, a Blakley secret sharing function, and a Rabin information dispersal algorithm (IDA) secret sharing function.