5 SSI architecture: the big picture
The purpose of this chapter is to take the basic building blocks, usage scenarios, features and benefits of SSI that we introduced in Part 1 and place them into an overarching picture of SSI architecture. As we will keep repeating, SSI is young, and many facets are still evolving. Still, the basic layering has emerged, along with several of the key underpinning standards, so the main questions are about how they will be implemented and how interoperable they will be depending on the design choices. In this chapter, Daniel Hardman, Chief Architect and CISO at Evernymm and a contributor to most of the core standards and protocols discussed here, will walk you through four layers of SSI architecture, the key components and technologies at each layer, and the critical design decisions facing architects and implementers throughout the “stack.” This chapter sets the stage for the rest of the chapters in Part 2 that dive deeper into specific SSI technologies.
In chapter 2 we discussed the basic building blocks of self-sovereign identity (SSI). Those building blocks represent important commonality—all approaches to the problem agree on them. However, like automobile design in the early 1900s, the young market is producing much innovation and divergence in the details. Some are inventing with two wheels, some with four or three. Some favor steam, while others favor internal combustion engines powered by gasoline or diesel.