diff --git a/src/ec/suite_b/ecdsa/signing.rs b/src/ec/suite_b/ecdsa/signing.rs
index 5c2547aaf5..dc72879712 100644
--- a/src/ec/suite_b/ecdsa/signing.rs
+++ b/src/ec/suite_b/ecdsa/signing.rs
@@ -153,6 +153,8 @@ impl EcdsaKeyPair {
 
     /// Returns the signature of the `message` using a random nonce
     /// generated by `rng`.
+    ///
+    /// The `message` is digested with the appropriate algorithm.
     pub fn sign(
         &self,
         rng: &dyn rand::SecureRandom,
@@ -163,6 +165,23 @@ impl EcdsaKeyPair {
         self.sign_(rng, h)
     }
 
+    /// Returns the signature of the `digest` using a random nonce
+    /// generated by `rng`.
+    ///
+    /// The `digest` algorithm must match that of the signing algorithm.
+    pub fn sign_digest(
+        &self,
+        rng: &dyn rand::SecureRandom,
+        digest: digest::Digest,
+    ) -> Result<signature::Signature, error::Unspecified> {
+        // Step 4 (out of order, already performed by caller).
+        if digest.algorithm() == self.alg.digest_alg {
+            self.sign_(rng, digest)
+        } else {
+            Err(error::Unspecified)
+        }
+    }
+
     /// Returns the signature of message digest `h` using a "random" nonce
     /// generated by `rng`.
     fn sign_(
@@ -435,6 +454,44 @@ mod tests {
         );
     }
 
+    #[test]
+    fn signature_ecdsa_sign_digest_fixed_test() {
+        test::run(
+            test_file!("ecdsa_sign_fixed_tests.txt"),
+            |section, test_case| {
+                assert_eq!(section, "");
+
+                let curve_name = test_case.consume_string("Curve");
+                let digest_name = test_case.consume_string("Digest");
+                let msg = test_case.consume_bytes("Msg");
+                let d = test_case.consume_bytes("d");
+                let q = test_case.consume_bytes("Q");
+                let k = test_case.consume_bytes("k");
+
+                let expected_result = test_case.consume_bytes("Sig");
+
+                let alg = match (curve_name.as_str(), digest_name.as_str()) {
+                    ("P-256", "SHA256") => &signature::ECDSA_P256_SHA256_FIXED_SIGNING,
+                    ("P-384", "SHA384") => &signature::ECDSA_P384_SHA384_FIXED_SIGNING,
+                    _ => {
+                        panic!("Unsupported curve+digest: {}+{}", curve_name, digest_name);
+                    }
+                };
+
+                let private_key =
+                    signature::EcdsaKeyPair::from_private_key_and_public_key(alg, &d, &q).unwrap();
+                let rng = test::rand::FixedSliceRandom { bytes: &k };
+
+                let digest = crate::digest::digest(alg.digest_alg, &msg);
+                let actual_result = private_key.sign_digest(&rng, digest).unwrap();
+
+                assert_eq!(actual_result.as_ref(), &expected_result[..]);
+
+                Ok(())
+            },
+        );
+    }
+
     #[test]
     fn signature_ecdsa_sign_asn1_test() {
         test::run(
@@ -471,4 +528,42 @@ mod tests {
             },
         );
     }
+
+    #[test]
+    fn signature_ecdsa_sign_digest_asn1_test() {
+        test::run(
+            test_file!("ecdsa_sign_asn1_tests.txt"),
+            |section, test_case| {
+                assert_eq!(section, "");
+
+                let curve_name = test_case.consume_string("Curve");
+                let digest_name = test_case.consume_string("Digest");
+                let msg = test_case.consume_bytes("Msg");
+                let d = test_case.consume_bytes("d");
+                let q = test_case.consume_bytes("Q");
+                let k = test_case.consume_bytes("k");
+
+                let expected_result = test_case.consume_bytes("Sig");
+
+                let alg = match (curve_name.as_str(), digest_name.as_str()) {
+                    ("P-256", "SHA256") => &signature::ECDSA_P256_SHA256_ASN1_SIGNING,
+                    ("P-384", "SHA384") => &signature::ECDSA_P384_SHA384_ASN1_SIGNING,
+                    _ => {
+                        panic!("Unsupported curve+digest: {}+{}", curve_name, digest_name);
+                    }
+                };
+
+                let private_key =
+                    signature::EcdsaKeyPair::from_private_key_and_public_key(alg, &d, &q).unwrap();
+                let rng = test::rand::FixedSliceRandom { bytes: &k };
+
+                let digest = crate::digest::digest(alg.digest_alg, &msg);
+                let actual_result = private_key.sign_digest(&rng, digest).unwrap();
+
+                assert_eq!(actual_result.as_ref(), &expected_result[..]);
+
+                Ok(())
+            },
+        );
+    }
 }