diff --git a/src/main/java/com/ning/maven/plugins/duplicatefinder/ClasspathDescriptor.java b/src/main/java/com/ning/maven/plugins/duplicatefinder/ClasspathDescriptor.java
index b1e6ada..8e9d7fe 100644
--- a/src/main/java/com/ning/maven/plugins/duplicatefinder/ClasspathDescriptor.java
+++ b/src/main/java/com/ning/maven/plugins/duplicatefinder/ClasspathDescriptor.java
@@ -19,10 +19,9 @@
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.io.InputStream;
-import java.util.AbstractMap;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
@@ -33,10 +32,8 @@
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
 import java.util.zip.ZipEntry;
-import java.util.zip.ZipInputStream;
-
+import java.util.zip.ZipFile;
 import org.apache.commons.io.FilenameUtils;
-import org.apache.commons.io.IOUtils;
 import org.apache.maven.plugin.MojoExecutionException;
 
 public class ClasspathDescriptor
@@ -192,16 +189,14 @@ private void addArchive(File element) throws IOException
 
         List classes = new ArrayList();
         List resources = new ArrayList();
-        InputStream    input    = null;
-        ZipInputStream zipInput = null;
+        ZipFile zipFile = null;
 
         try {
-            input    = element.toURI().toURL().openStream();
-            zipInput = new ZipInputStream(input);
-
-            ZipEntry entry;
+            zipFile = new ZipFile(element);
+            Enumeration entries = zipFile.entries();
 
-            while ((entry = zipInput.getNextEntry()) != null) {
+            while (entries.hasMoreElements()) {
+                ZipEntry entry = (ZipEntry) entries.nextElement();
                 if (!entry.isDirectory()) {
                     String name = entry.getName();
 
@@ -223,12 +218,13 @@ private void addArchive(File element) throws IOException
             CACHED_BY_ELEMENT.put(element, new Cached(classes, resources));
         }
         finally {
-            if (zipInput != null) {
-                // this will also close the wrapped stream
-                IOUtils.closeQuietly(zipInput);
-            }
-            else if (input != null) {
-                IOUtils.closeQuietly(input);
+            // IOUtils has no closeQuietly for Closable in the 1.x series.
+            if (zipFile != null) {
+                try {
+                    zipFile.close();
+                } catch (IOException ex) {
+                    // ignored
+                }
             }
         }
     }
diff --git a/src/main/java/com/ning/maven/plugins/duplicatefinder/DuplicateFinderMojo.java b/src/main/java/com/ning/maven/plugins/duplicatefinder/DuplicateFinderMojo.java
index fbc7fcf..a25b8eb 100644
--- a/src/main/java/com/ning/maven/plugins/duplicatefinder/DuplicateFinderMojo.java
+++ b/src/main/java/com/ning/maven/plugins/duplicatefinder/DuplicateFinderMojo.java
@@ -60,6 +60,8 @@ public class DuplicateFinderMojo extends AbstractMojo
 {
     protected final Logger LOG = LoggerFactory.getLogger(this.getClass());
 
+    private static Map CACHED_SHA256 = new HashMap();
+
     // the constants for conflicts
     private final static int NO_CONFLICT = 0;
     private final static int CONFLICT_CONTENT_EQUAL = 1;
@@ -423,6 +425,34 @@ else if(!newSHA256.equals(firstSHA256)) {
      */
     private String getSHA256HexOfElement(final File file, final String resourcePath) throws IOException
     {
+        class Sha256CacheKey {
+            final File file;
+            final String resourcePath;
+
+            Sha256CacheKey(File file, String resourcePath) {
+                this.file = file;
+                this.resourcePath = resourcePath;
+            }
+
+            public boolean equals(Object o) {
+                if (this == o) return true;
+                if (o == null || getClass() != o.getClass()) return false;
+
+                Sha256CacheKey key = (Sha256CacheKey) o;
+
+                return file.equals(key.file) && resourcePath.equals(key.resourcePath);
+            }
+
+            public int hashCode() {
+                return 31 * file.hashCode() + resourcePath.hashCode();
+            }
+        }
+
+        final Sha256CacheKey key = new Sha256CacheKey(file, resourcePath);
+        if (CACHED_SHA256.containsKey(key)) {
+            return (String) CACHED_SHA256.get(key);
+        }
+
     	ZipFile zip = new ZipFile(file);
     	ZipEntry zipEntry = zip.getEntry(resourcePath);
     	if(zipEntry == null)
@@ -439,6 +469,8 @@ private String getSHA256HexOfElement(final File file, final String resourcePath)
 		} finally {
 			IOUtils.closeQuietly(in);
 		}
+
+        CACHED_SHA256.put(key, sha256);
     		
     	return sha256;
     }