A reference implementation for the Path ORAM. For a description of the algorithm, please refer to https://eprint.iacr.org/2013/280.pdf

Requirements

C++17 is required. Known to compile with gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1) and gcc version 7.3.1 20180130 (Red Hat 7.3.1-2) (GCC).

Files

All .cpp files are in the src/ and all .h files are in the include/ directory, including any interfaces. test/ contains various tests using the catch2 C++ testing framework.

Block, Bucket: contain implementations for the Block and Bucket data structures as described in the paper.

include/UntrustedStorageInterface: defines the interface that the Path ORAM implemenation uses to communicate with the untrusted cloud storage provider. A possible implementation is defined in ServerStorage.

include/RandForOramInterface: the Path ORAM implementation gets random leaf ids from here. A possible implementation is defined in RandomForOram. Can be overridden e.g. for testing purposes.

include/OramInterface: The interface with which to use this Path ORAM implementation. OramReadPathEviction and OramDeterministic contain two implementations of the eviction.

OramReadPathEviction: contains an eviction algorithm which writes back to the accessed path.

OramDeterministic: contains reverse lexicographical re-writes of paths.

CorrectnessTesterXX: contain correctness tests for the read and write, also runtime demonstrations of the stash size.

main: Can be used to run any of the above tests.

csprng.cpp and include/duthomhas/: This file and directory contain code from the CSPRNG library as per the suggestion in the library's github.

Compiling and Running

To compile the implementation, run make in the PORAM directory. To run the code in main.cpp, you may now call ./PORAMRun.

To compile and run tests for the first time:

1. Call make and then make test_full.
2. Run the tests by running ./PORAMTest.

To compile and run tests any subsequent time:

1. Call make if you changed any of the files in src/.
2. Call make test to make the tests and ./PORAMTest to run all the tests.

Adding Tests

Tests running using catch2 are located in the test/ respository. To add new tests, add a new .cpp file to the test/ directory. You must include catch.h in any new test files. The include/ directory is already linked by the make file, to include any files from the implementation in your tests, include their headers. See any of the current test files or the catch2 documentation to get a template for test cases.

Running make test as before will also compile any new test cases.

Randomness

Note that the instantiation of RandForOramInterface in RandomForOram uses the CSPRNG code by Michael Thomas Greer which provides cryptographically secure PRNGs for both Linux and Windows. The file also includes an implementation using the standard C++ implementation of the Mersenne Twister Engine (MT) to instantiate the random number generator. Finally, it also contains an implementation of the LCG random number generator, instantiated using the same parameters as used in the standard Java implementation. The MT and LCG implementations could be useful when comparing outputs of this implementation (or code that uses it) with the outputs of another implementation using the same PRNGs with the same seeds.