# Inter-Rollup and Inter-Protocol Bridges Proof-carrying data refers to the process of providing a zk-SNARK as input to an arithmetic circuit in order to produce another zk-SNARK which validates the input zk-SNARK. Proof-carrying data and recursive proofs, as well as zk-SNARKs more generally, are useful concepts for creating interoperability between different trustless protocols. One design principle of Orbis is that all the world’s demand for zk-rollups could be met by one rollup. In reality, more than one zk-rollup will exist and an open decentralized financial ecosystem cannot become a reality without protocols for interoperability between decentralized protocols. The concept similar to sending a UTxO between heterogeneous Orbis rollups can be applied to create bridges between zk-rollup protocols based on different zk-SNARK theories. Applying the concepts requires only that 1. A zk-SNARK can be created proving the creation of a UTxO burning transaction in the source protocol. 2. A zk-SNARK can be validated as part of the conditions for validating a UTxO factory transaction in the destination protocol. The concept of inter-protocol bridges opens the door to a concept of layer 3 rollups, which are rollups that use an L2 rollup in place of an L1 blockchain as the basis for the settlement and commitment protocol. Layer 3 rollups may be useful for specialized applications. This concept could be further extended to layer 4 rollups and beyond. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.orbisprotocol.com/orbis/inter-rollup-and-inter-protocol-bridges.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.