Added implementation of https://eprint.iacr.org/2024/1077

[sandy9999]

Added implementation of the Decision Tree protocol from "Securely Training Decision Trees Efficiently" by Divyanshu Bhardwaj, Sandhya Saravanan, Nishanth Chandran and Divya Gupta : eprint link.

This decision tree training protocol has communication complexity $O(mN \log N + hmN + hN \log N)$ which is an improvement of $\approx min(h, m, \log N)$ over Hamada et. al link.

-Sandhya Saravanan

[mkskeller]

Thank you for submitting this pull request. However, the code isn't suitable for inclusion due to the following reasons:

• Using the code fails with an indentation error
• If the error is corrected, it fails because radix_sort_permutation_from_matrix is not available
• I don't see a good reason for a separate module if the functionality it provides is essentially the same as an existing module
• decision_tree_new is not a meaningful name and will be even less meaningful as time goes on
• Multiple functions are just copy-pasted instead of imported. This is bad practice as future improvements to them will go unused.

I would suggest the following apart from correcting the compilation errors:

• Add the code to the decision_tree module where it can be found by users.
• Avoid using "new" as prefix or suffix. Use either "optimized" or something more prescriptive.
• Avoid the use of entirely copy-pasted functions.
• Consider sub-classing the existing classes.