diff --git a/signature-crate/Cargo.toml b/signature-crate/Cargo.toml
index 773be118..f52a60af 100644
--- a/signature-crate/Cargo.toml
+++ b/signature-crate/Cargo.toml
@@ -12,8 +12,9 @@ keywords      = ["crypto", "ecdsa", "ed25519", "signature", "signing"]
 categories    = ["cryptography", "no-std"]
 
 [dependencies]
+digest = { version = "0.8", optional = true, default-features = false }
 
 [features]
-default = ["std"]
+default = ["digest", "std"]
 alloc   = []
 std     = ["alloc"]
diff --git a/signature-crate/src/lib.rs b/signature-crate/src/lib.rs
index 85ccc2bd..14d15ddf 100644
--- a/signature-crate/src/lib.rs
+++ b/signature-crate/src/lib.rs
@@ -14,12 +14,17 @@
     unused_qualifications
 )]
 
+#[cfg(feature = "digest")]
+pub extern crate digest;
+
 #[cfg(any(feature = "std", test))]
 #[macro_use]
 extern crate std;
 
 mod error;
 mod prelude;
+pub mod sign;
 mod signature;
+pub mod verify;
 
-pub use crate::{error::Error, signature::Signature};
+pub use crate::{error::Error, sign::Sign, signature::Signature, verify::Verify};
diff --git a/signature-crate/src/sign/digest.rs b/signature-crate/src/sign/digest.rs
new file mode 100644
index 00000000..e4f21c2b
--- /dev/null
+++ b/signature-crate/src/sign/digest.rs
@@ -0,0 +1,18 @@
+//! Support for signing messages which have been prehashed messages using
+//! the `Digest` trait.
+//!
+//! For use signature algorithms that support an Initialize-Update-Finalize
+//! (IUF) API, such as ECDSA or Ed25519ph.
+
+use crate::{error::Error, Signature};
+use digest::Digest;
+
+/// Sign the given prehashed message `Digest` using `Self`.
+pub trait SignDigest<D, S>: Send + Sync
+where
+    D: Digest,
+    S: Signature,
+{
+    /// Sign the given prehashed message `Digest`, returning a signature.
+    fn sign(&self, digest: D) -> Result<S, Error>;
+}
diff --git a/signature-crate/src/sign/mod.rs b/signature-crate/src/sign/mod.rs
new file mode 100644
index 00000000..1acc7c84
--- /dev/null
+++ b/signature-crate/src/sign/mod.rs
@@ -0,0 +1,15 @@
+//! Traits for generating digital signatures
+
+#[cfg(feature = "digest")]
+pub(crate) mod digest;
+
+#[cfg(feature = "digest")]
+pub use self::digest::SignDigest;
+use crate::{error::Error, Signature};
+
+/// Sign the provided message bytestring using `Self` (e.g. a cryptographic key
+/// or connection to an HSM), returning a digital signature.
+pub trait Sign<S: Signature>: Send + Sync {
+    /// Sign the given message and return a digital signature
+    fn sign(&self, msg: &[u8]) -> Result<S, Error>;
+}
diff --git a/signature-crate/src/verify/digest.rs b/signature-crate/src/verify/digest.rs
new file mode 100644
index 00000000..c577e700
--- /dev/null
+++ b/signature-crate/src/verify/digest.rs
@@ -0,0 +1,19 @@
+//! Support for verifying messages which have been prehashed messages using
+//! the `Digest` trait.
+//!
+//! For use signature algorithms that support an Initialize-Update-Finalize
+//! (IUF) API, such as ECDSA or Ed25519ph.
+
+use crate::{error::Error, Signature};
+use digest::Digest;
+
+/// Verify the provided signature for the given prehashed message `Digest`
+/// is authentic.
+pub trait VerifyDigest<D, S>: Send + Sync
+where
+    D: Digest,
+    S: Signature,
+{
+    /// Verify the signature against the given `Digest`
+    fn verify(&self, digest: D, signature: &S) -> Result<(), Error>;
+}
diff --git a/signature-crate/src/verify/mod.rs b/signature-crate/src/verify/mod.rs
new file mode 100644
index 00000000..d8c4b0e2
--- /dev/null
+++ b/signature-crate/src/verify/mod.rs
@@ -0,0 +1,17 @@
+//! Trait for verifying digital signatures
+
+#[cfg(feature = "digest")]
+pub(crate) mod digest;
+
+#[cfg(feature = "digest")]
+pub use self::digest::VerifyDigest;
+use crate::{error::Error, Signature};
+
+/// Verify the provided message bytestring using `Self` (e.g. a public key)
+pub trait Verify<S: Signature>: Send + Sync {
+    /// Use `Self` to verify that the provided signature for a given message
+    /// bytestring is authentic.
+    ///
+    /// Returns `Error` if it is inauthentic, or otherwise returns `()`.
+    fn verify(&self, msg: &[u8], signature: &S) -> Result<(), Error>;
+}