Blockchain Commons Blockchain Commons Universität Bremen TZI Security Theory LLC The purpose of determinism is to ensure that semantically equivalent data items are encoded into identical byte streams. CBOR (RFC 8949) defines "Deterministically Encoded CBOR" in its Section 4.2, but leaves some important choices up to the application developer. The present document specifies dCBOR, a set of narrowing rules for CBOR that can be used to help achieve interoperable deterministic encoding for a variety of applications desiring a narrow and clearly defined set of choices.