A Formal Approach for the Analysis of the XRP Ledger Consensus Protocol

Distributed ledger technology is envisioned as one of the cornerstones of promising solutions for building the next generation of critical applications. However, there is still quite a bit of confusion and hype around the real security guarantees this technology offers. This is especially due to the fact that for the vast majority of existing blockchain-based consensus protocols it is really hard to find sufficiently detailed documentation that fully captures their behavior. A number of recent papers have formalized the behavior of Bitcoin-like protocols in order to rigorously study the security and privacy properties of their underlying structure, but surprisingly very little work has been devoted to the formalization of distributed ledger systems using BFT-like approaches. In this work, we focus on XRP Ledger, better known as Ripple, and take the first steps towards the complete formalization of its consensus protocol. To this end, we have investigated all the existing documentation and analyzed its source code. We present a formal description of its consensus protocol for every step. Furthermore, we provide an accurate view of its security guarantees in terms of safety and liveness and show how to increase the desired tolerance by changing the value of specific protocol parameters.