elliptic-curve: basic OID support

Adds a (very simple, const-and-no_std-friendly) `ObjectIdentifier` type
and an `Identifier` trait for attaching an OID to a curve.

No validation of the nodes is presently performed (and since it's impl'd
as a `const fn`, it'd require a MSRV bump to do so). Also requires the
OID be specified as an array literal: no parsing is supported for either
string or binary-encoded OIDs.

Only string serialization is supported for now. A `no_std`-friendly
binary serializer will be somewhat tricky.

elliptic-curve/src/lib.rs

@@ -22,6 +22,7 @@
 extern crate std;
 
 pub mod error;
+pub mod oid;
 pub mod ops;
 pub mod secret_key;
 
@@ -30,7 +31,7 @@ pub mod secret_key;
 #[cfg_attr(docsrs, doc(cfg(feature = "weierstrass")))]
 pub mod weierstrass;
 
-pub use self::{error::Error, secret_key::SecretKey};
+pub use self::{error::Error, oid::ObjectIdentifier, secret_key::SecretKey};
 pub use generic_array::{self, typenum::consts};
 pub use subtle;
 
@@ -72,6 +73,12 @@ pub trait Arithmetic: Curve {
  type AffinePoint: ConditionallySelectable + ops::MulBase<Scalar = Self::Scalar>;
 }
 
+/// Associate an object identifier (OID) with a curve
+pub trait Identifier: Curve {
+ /// Object Identifier (OID) for this curve
+ const OID: ObjectIdentifier;
+}
+
 /// Randomly generate a value.
 ///
 /// Primarily intended for use with scalar types for a particular curve.

elliptic-curve/src/oid.rs

@@ -0,0 +1,48 @@
+//! Object identifiers (OIDs)
+
+use core::fmt;
+
+/// Object identifier (OID)
+pub struct ObjectIdentifier(&'static [u32]);
+
+impl ObjectIdentifier {
+ /// Create a new OID
+ pub const fn new(nodes: &'static [u32]) -> Self {
+ // TODO(tarcieri): validate nodes
+ Self(nodes)
+ }
+}
+
+impl AsRef<[u32]> for ObjectIdentifier {
+ fn as_ref(&self) -> &[u32] {
+ self.0
+ }
+}
+
+impl fmt::Display for ObjectIdentifier {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ for (i, node) in self.0.iter().enumerate() {
+ write!(f, "{}", node)?;
+
+ if i < self.0.len() - 1 {
+ write!(f, ".")?;
+ }
+ }
+
+ Ok(())
+ }
+}
+
+#[cfg(all(test, std))]
+mod tests {
+ use super::ObjectIdentifier;
+ use std::string::ToString;
+
+ const EXAMPLE_OID: ObjectIdentifier = ObjectIdentifier::new(&[1, 2, 840, 10045, 3, 1, 7]);
+
+ #[test]
+ fn display_test() {
+ let oid = EXAMPLE_OID.to_string();
+ assert_eq!(oid, "1.2.840.10045.3.1.7");
+ }
+}