diff --git a/apub-openssl/src/lib.rs b/apub-openssl/src/lib.rs
index e6df060..4c14aed 100644
--- a/apub-openssl/src/lib.rs
+++ b/apub-openssl/src/lib.rs
@@ -36,18 +36,12 @@ impl OpenSsl {
     }
 }
 
-impl<'a> apub_core::digest::Digest for OpenSslDigest {
+impl apub_core::digest::Digest for OpenSslDigest {
     const NAME: &'static str = "SHA-256";
 
-    fn build() -> Self {
-        OpenSslDigest {
-            digest: Sha256::new(),
-        }
-    }
-
-    fn digest(mut self, input: &[u8]) -> String {
+    fn digest(&mut self, input: &[u8]) -> String {
         self.digest.update(input);
-        let bytes = self.digest.finish();
+        let bytes = self.digest.clone().finish();
 
         openssl::base64::encode_block(&bytes)
     }
@@ -56,13 +50,21 @@ impl<'a> apub_core::digest::Digest for OpenSslDigest {
         self.digest.update(input);
     }
 
-    fn verify(self, encoded: &str) -> bool {
-        let bytes = self.digest.finish();
+    fn verify(&mut self, encoded: &str) -> bool {
+        let bytes = self.digest.clone().finish();
 
         openssl::base64::encode_block(&bytes) == encoded
     }
 }
 
+impl apub_core::digest::DigestBuilder for OpenSslDigest {
+    fn build() -> Self {
+        OpenSslDigest {
+            digest: Sha256::new(),
+        }
+    }
+}
+
 impl apub_core::signature::Sign for OpenSslSigner {
     type Error = ErrorStack;
 
@@ -77,6 +79,14 @@ impl apub_core::signature::Sign for OpenSslSigner {
 impl apub_core::signature::Verify for OpenSslVerifier {
     type Error = ErrorStack;
 
+    fn verify(&self, signing_string: &str, signature: &str) -> Result<bool, Self::Error> {
+        let mut verifier = Verifier::new(MessageDigest::sha256(), &self.public_key)?;
+        verifier.update(signing_string.as_bytes())?;
+        Ok(verifier.verify(&openssl::base64::decode_block(&signature)?)?)
+    }
+}
+
+impl apub_core::signature::VerifyBuilder for OpenSslVerifier {
     fn build(public_key_pem: &str) -> Result<Self, Self::Error>
     where
         Self: Sized,
@@ -85,12 +95,6 @@ impl apub_core::signature::Verify for OpenSslVerifier {
             public_key: PKey::public_key_from_pem(public_key_pem.as_bytes())?,
         })
     }
-
-    fn verify(&self, signing_string: &str, signature: &str) -> Result<bool, Self::Error> {
-        let mut verifier = Verifier::new(MessageDigest::sha256(), &self.public_key)?;
-        verifier.update(signing_string.as_bytes())?;
-        Ok(verifier.verify(&openssl::base64::decode_block(&signature)?)?)
-    }
 }
 
 impl apub_core::digest::DigestFactory for OpenSsl {