diff --git a/apub-core/src/deliver.rs b/apub-core/src/deliver.rs
index ffddfba..45e83ea 100644
--- a/apub-core/src/deliver.rs
+++ b/apub-core/src/deliver.rs
@@ -5,9 +5,6 @@ pub trait Client<'a> {
     type Error: std::error::Error + 'static;
     type Future: Future<Output = Result<(), Self::Error>> + 'a;
 
-    fn deliver<'b, T: serde::ser::Serialize>(
-        &'b self,
-        inbox: &'a Url,
-        activity: &'a T,
-    ) -> Self::Future;
+    fn deliver<T: serde::ser::Serialize>(&'a self, inbox: &'a Url, activity: &'a T)
+        -> Self::Future;
 }
diff --git a/apub-core/src/digest.rs b/apub-core/src/digest.rs
index 8e9a3e9..4709868 100644
--- a/apub-core/src/digest.rs
+++ b/apub-core/src/digest.rs
@@ -1,11 +1,10 @@
 pub trait Digest {
     const NAME: &'static str;
 
+    fn build() -> Self;
     fn digest(self, input: &[u8]) -> String;
 }
 
 pub trait DigestFactory {
     type Digest: Digest + Send;
-
-    fn digest(&self) -> Self::Digest;
 }
diff --git a/apub-core/src/signature.rs b/apub-core/src/signature.rs
index bc4a0f6..f78f4b2 100644
--- a/apub-core/src/signature.rs
+++ b/apub-core/src/signature.rs
@@ -17,11 +17,13 @@ pub trait SignFactory {
 pub trait Verify {
     type Error: std::error::Error + Send;
 
+    fn build(public_key_pem: &str) -> Result<Self, Self::Error>
+    where
+        Self: Sized;
+
     fn verify(&self, signing_string: &str, signature: &str) -> Result<bool, Self::Error>;
 }
 
 pub trait VerifyFactory {
     type Verifier: Verify + Send + 'static;
-
-    fn verifier(&self, public_key_pem: String) -> Self::Verifier;
 }