When you are pitching to venture capitalists, it will be the rare exception where you can expect any sort of confidentiality. VCs will act in their own interests, and if they think that leaking/sharing something you told them will help make them money, they will do it.
They don't care about the details of your algorithms. They probably won't understand what you say anyway. They only care about what your technology will do for them (i.e. make them piles money).
More important than any technical details is the assurance that you can protect yourself from copycats.
And of course they also want some assurance that you can be trusted to make money with their money, should they give it to you.
Use your PowerPoint deck to tell them about your past successes, your credentials, your well researched business plan, how you are uniquely qualified to make their investors money, and how much interest you've been getting from competing sources of funding.