VDF for Better Blocks's Execution Budget

[jio-gl]

In terms of VDF two of the better established are Pietrzak and Wesolowski (implementation in Rust here https://github.com/poanetwork/vdf/tree/master/vdf). Also if you have short block times, for example 15 second blocktime but not suitable for 10 minute blocks probably, you can use Sloth VDF that is a pseudo-VDF that has 400x to 800x more speed on generating the proof than verifying it. It is a pseudo-VDF because verification scales as fast as proof generation but is 400-800 times faster. Here is variant of Sloth pseudo-VDF written in Rust (https://github.com/subspace/spartan-codec).
Here is a performance analyzis of Pietrazak and Wesolowki VDF algos (https://medium.com/supranational/open-vdf-vdf-proof-techniques-157a5a3db4c2):

The Wesolowski proof has higher computational cost to generate but produces smaller proofs with constant and cheap verification time. The Pietrzak proof has lower computational cost but produces larger proofs with variable and longer verification time. Since Wesolowski has improved characteristics for a blockchain setting we'll start by analyzing it, and then consider whether Pietrzak can or should play a role.