resolve Sean's comments; some small utility method updates

src/java.base/share/classes/sun/security/provider/NamedSignature.java

@@ -55,12 +55,12 @@ public abstract class NamedSignature extends SignatureSpi {
     private final ByteArrayOutputStream bout = new ByteArrayOutputStream();
 
     // init with...
-    private String name = null;
-    private byte[] secKey = null;
-    private byte[] pubKey = null;
+    private String name;
+    private byte[] secKey;
+    private byte[] pubKey;
 
-    private Object sk2 = null;
-    private Object pk2 = null;
+    private Object sk2;
+    private Object pk2;
 
     /// Creates a new `NamedSignature` object.
     ///
@@ -118,7 +118,7 @@ protected byte[] engineSign() throws SignatureException {
             bout.reset();
             return implSign(name, secKey, sk2, msg, appRandom);
         } else {
-            throw new IllegalStateException("No private key");
+            throw new SignatureException("No private key");
         }
     }
 
@@ -129,21 +129,21 @@ protected boolean engineVerify(byte[] sig) throws SignatureException {
             bout.reset();
             return implVerify(name, pubKey, pk2, msg, sig);
         } else {
-            throw new IllegalStateException("No public key");
+            throw new SignatureException("No public key");
         }
     }
 
     @Override
     @SuppressWarnings("deprecation")
     protected void engineSetParameter(String param, Object value)
             throws InvalidParameterException {
-        throw new UnsupportedOperationException("setParameter() not supported");
+        throw new InvalidParameterException("setParameter() not supported");
     }
 
     @Override
     @SuppressWarnings("deprecation")
     protected Object engineGetParameter(String param) throws InvalidParameterException {
-        throw new UnsupportedOperationException("getParameter() not supported");
+        throw new InvalidParameterException("getParameter() not supported");
     }
 
     @Override
@@ -188,9 +188,9 @@ protected abstract boolean implVerify(String name, byte[] pk, Object pk2,
 
     /// User-defined function to validate a public key.
     ///
-    /// This method will be called in `initVerify`. This gives provider a chance to
+    /// This method will be called in `initVerify`. This gives the provider a chance to
     /// reject the key so an `InvalidKeyException` can be thrown earlier.
-    /// An implementation can optional return a "parsed key" as an `Object` value.
+    /// An implementation can optionally return a "parsed key" as an `Object` value.
     /// This object will be passed into the [#implVerify] method along with the raw key.
     ///
     /// The default implementation returns `null`.
@@ -205,9 +205,9 @@ protected Object implCheckPublicKey(String name, byte[] pk) throws InvalidKeyExc
 
     /// User-defined function to validate a private key.
     ///
-    /// This method will be called in `initSign`. This gives provider a chance to
+    /// This method will be called in `initSign`. This gives the provider a chance to
     /// reject the key so an `InvalidKeyException` can be thrown earlier.
-    /// An implementation can optional return a "parsed key" as an `Object` value.
+    /// An implementation can optionally return a "parsed key" as an `Object` value.
     /// This object will be passed into the [#implSign] method along with the raw key.
     ///
     /// The default implementation returns `null`.

src/java.base/share/classes/sun/security/util/KeyUtil.java

@@ -184,13 +184,13 @@ public static final int getKeySize(AlgorithmParameters parameters) {
      */
     public static final String fullDisplayAlgName(Key key) {
         String result = key.getAlgorithm();
-        if (key instanceof ECKey) {
-            ECParameterSpec paramSpec = ((ECKey) key).getParams();
+        if (key instanceof AsymmetricKey ak) {
+            AlgorithmParameterSpec paramSpec = ak.getParams();
             if (paramSpec instanceof NamedCurve nc) {
                 result += " (" + nc.getNameAndAliases()[0] + ")";
+            } else if (paramSpec instanceof NamedParameterSpec nps) {
+                result = nps.getName();
             }
-        } else if (key instanceof EdECKey) {
-            result = ((EdECKey) key).getParams().getName();
         }
         return result;
     }

src/java.base/share/classes/sun/security/util/SignatureUtil.java

@@ -274,7 +274,7 @@ public static String extractDigestAlgFromDwithE(String signatureAlgorithm) {
             return signatureAlgorithm.substring(0, with);
         } else {
             throw new IllegalArgumentException(
-                    "Unknown algorithm: " + signatureAlgorithm);
+                    "Cannot extract digest algorithm from " + signatureAlgorithm);
         }
     }
 
@@ -495,8 +495,10 @@ public static String getDefaultSigAlgForKey(PrivateKey k) {
             case "EDDSA" -> k instanceof EdECPrivateKey
                     ? ((EdECPrivateKey) k).getParams().getName()
                     : kAlg;
-            default -> kAlg; // All modern signature algorithms,
-                             // RSASSA-PSS, ED25519, ED448, HSS/LMS, etc
+            default -> kAlg.contains("KEM") ? null : kAlg;
+                // All modern signature algorithms use the same name across
+                // key algorithms and signature algorithms, for example,
+                // RSASSA-PSS, ED25519, ED448, HSS/LMS, etc
         };
     }