>First, cryptographic signing and identity management exists today, and long before blockchain was ever even proposed. It’s SSL and other public key encryption

>First, cryptographic signing and identity management exists today, and long before blockchain was ever even proposed. It’s SSL and other public key encryption systems. Which fail to provide the capability based security required for a Xanadu-like project. You might want to read about the Confused Deputy Problem for starters: https://en.wikipedia.org/wiki/Confused_deputy_problem https://en.wikipedia.org/wiki/Confused_deputy_problem There exist other approaches for avoiding the confused deputy problem, but these don't have mutual exclusivity with capability based security, one such approach consists of something like this: https://github.com/phvogt/NoMoXSS https://github.com/phvogt/NoMoXSS Which basically uses this concept: https://en.wikipedia.org/wiki/Taint_checking https://en.wikipedia.org/wiki/Taint_checking However, that leads us right back into another Xanadu related problem: https://en.wikipedia.org/wiki/Trademark_(computer_security) https://en.wikipedia.org/wiki/Trademark_(computer_security) Think about why we call this a "Trademark", and what that means for concepts like transcopyright licensing such as the one required for Xanadu. If you look into who advised on & worked on Xanadu, you'll find names like Mark S. Miller: https://en.wikipedia.org/wiki/Mark_S._Miller https://en.wikipedia.org/wiki/Mark_S._Miller ...whose name you'll find popping up all over the object capability security literature. That ain't a coincidence. The shortcomings Xanadu tries to address and which conversely Xanadu requires to have addressed before it can come about pervade computer science, everywhere.