Fixing Cryptographic Edge Case test on Java 21+.

Author: coheigea

src/test/java/org/apache/xml/security/test/dom/algorithms/CryptographicEdgeCasesTest.java

@@ -26,6 +26,7 @@
 
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
+import java.security.interfaces.RSAPublicKey;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -79,8 +80,9 @@ void testAllZerosSignatureRejected() throws Exception {
         // Initialize verification
         sa.initVerify(keyPair.getPublic());
 
-        // Create all-zeros signature (256 bytes for RSA-2048)
-        byte[] zeroSignature = new byte[256];
+        // Create all-zeros signature with the exact byte length expected for this key
+        int signatureLength = (((RSAPublicKey) keyPair.getPublic()).getModulus().bitLength() + 7) / 8;
+        byte[] zeroSignature = new byte[signatureLength];
 
         // Update with some data
         byte[] data = "test data".getBytes();