For research purposes, I want to know the following:
- What is the exact size of the set of already spent key images and how it can be checked? Do we need to download the Monero blockchain to get the size?
- Using the
is_key_image_spentapi, we can check if a key image is a member of the set of already spent key images or not. Can this set be made a zero-knowledge set using some accumulator so that a zero-knowledge set membership or non-membership proof can be given for a particular group element (key image) bypassing this api? Does there exist any accumulator suitable for this purpose?
Thanks in advance for your insights.