1 files changed, 48 insertions, 0 deletions
diff --git a/vendor/elliptic-curve/src/hash2curve/hash2field.rs b/vendor/elliptic-curve/src/hash2curve/hash2field.rs
new file mode 100644
index 000000000..6cd0723aa
--- /dev/null
+++ b/vendor/elliptic-curve/src/hash2curve/hash2field.rs
@@ -0,0 +1,48 @@
+//! Traits for hashing to field elements.
+//!
+//! <https://datatracker.ietf.org/doc/draft-irtf-cfrg-hash-to-curve>
+
+mod expand_msg;
+
+pub use expand_msg::{xmd::*, xof::*, *};
+
+use crate::Result;
+use generic_array::{typenum::Unsigned, ArrayLength, GenericArray};
+
+/// The trait for helping to convert to a field element.
+pub trait FromOkm {
+    /// The number of bytes needed to convert to a field element.
+    type Length: ArrayLength<u8>;
+
+    /// Convert a byte sequence into a field element.
+    fn from_okm(data: &GenericArray<u8, Self::Length>) -> Self;
+}
+
+/// Convert an arbitrary byte sequence into a field element.
+///
+/// <https://tools.ietf.org/html/draft-irtf-cfrg-hash-to-curve-11#section-5.3>
+///
+/// # Errors
+/// See implementors of [`ExpandMsg`] for errors:
+/// - [`ExpandMsgXmd`]
+/// - [`ExpandMsgXof`]
+///
+/// `len_in_bytes = T::Length * out.len()`
+///
+/// [`ExpandMsgXmd`]: crate::hash2field::ExpandMsgXmd
+/// [`ExpandMsgXof`]: crate::hash2field::ExpandMsgXof
+#[doc(hidden)]
+pub fn hash_to_field<'a, E, T>(data: &[&[u8]], domain: &'a [u8], out: &mut [T]) -> Result<()>
+where
+    E: ExpandMsg<'a>,
+    T: FromOkm + Default,
+{
+    let len_in_bytes = T::Length::to_usize() * out.len();
+    let mut tmp = GenericArray::<u8, <T as FromOkm>::Length>::default();
+    let mut expander = E::expand_message(data, domain, len_in_bytes)?;
+    for o in out.iter_mut() {
+        expander.fill_bytes(&mut tmp);
+        *o = T::from_okm(&tmp);
+    }
+    Ok(())
+}