Crate const_oid

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§RustCrypto: Object Identifiers (OIDs)

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Const-friendly implementation of the ISO/IEC Object Identifier (OID) standard as defined in ITU X.660, with support for BER/DER encoding/decoding as well as heapless no_std (i.e. embedded) environments.


§About OIDs

Object Identifiers, a.k.a. OIDs, are an International Telecommunications Union (ITU) and ISO/IEC standard for naming any object, concept, or “thing” with a globally unambiguous persistent name.

The ITU’s X.660 standard provides the OID specification. Every OID is part of a hierarchical namespace which begins with a root OID, which is either the ITU’s root OID (0), the ISO’s root OID (1), or the joint ISO/ITU root OID (2).

The following is an example of an OID, in this case identifying the rsaEncryption algorithm:


For more information, see:


This library supports parsing OIDs in const contexts, e.g.:

use const_oid::ObjectIdentifier;

pub const MY_OID: ObjectIdentifier = ObjectIdentifier::new_unwrap("1.2.840.113549.1.1.1");

The OID parser is implemented entirely in terms of const fn and without the use of proc macros.

Additionally, it also includes a const fn OID serializer, and stores the OIDs parsed from const contexts encoded using the BER/DER serialization (sans header).

This allows ObjectIdentifier to impl AsRef<[u8]> which can be used to obtain the BER/DER serialization of an OID, even one declared const.

Additionally, it impls FromStr and TryFrom<&[u8]> and functions just as well as a runtime OID library.

§Minimum Supported Rust Version

This crate requires Rust 1.57 at a minimum.

We may change the MSRV in the future, but it will be accompanied by a minor version bump.


Licensed under either of:

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.




  • A trait which associates an OID with a type.
  • A trait which associates a dynamic, &self-dependent OID with a type, which may change depending on the type’s value.

Type Aliases§

  • Type alias used to represent an “arc” (i.e. integer identifier value).
  • Result type