More explanations on Monero's implementation of bulletproofs could be found on youtube fondajo channel in a [conversation with Sarang Noether](https://www.youtube.com/watch?v=6lEWqIMLzUU).
OSTIF directed the group to several organizations with the skills required to perform the audit. While one of them asked to be kept unnamed and was therefore put away from the process that needed to be public, two others (QuarksLab & Kudelski Security) were choosen to conduct the audit.
Our 3 auditors were funded by the community to ensure that the implementation did not contain any critical bugs or exploits.The final reports were released during the summer of 2018, with several useful corrections and fixes suggested, and the final bulletproof implementation has been added first to Monero Stagenet, and then to the main Monero network during the October 2018 network upgrade.
@RingCT was introduced to obfuscate transaction amounts. One goal of @RingCT was to prove the sum of inputs - outputs in the @transaction was equal to 0, and all outputs were positive numbers.
The code has been written and rewritten to follow the new version of bulletproofs which was still being developed, but once this Monero implementation was finalized, the resulting deployment should be taken with extreme care.
Therefore, the community started an auditing process. Researchers reached out to Benedikt Bünz, lead author of the Bulletproofs paper, and to [OSTIF](https://ostif.org/) an organization which helps open source technologies to improve and secure themselves.
To accomplish this, two kind of ring signatures were constructed: One ring signature for the whole transaction (to prove the sum is 0), and a set of ring signatures for the subsets of transaction bits (to prove the outputs are positive numbers), then combined together using originally Schnorr signatures (and later replaced by Borromean ring signature).
