Excellent questions. We have encountered all of them in practice and have solutions for most of them, e.g., (4) requires an ACL-aware search index. Unfortunate

Excellent questions. We have encountered all of them in practice and have solutions for most of them, e.g., (4) requires an ACL-aware search index. Unfortunately we don't have enough space to explain them in the paper. Please consider coming to Usenix. :-)