diff --git a/pgpainless-core/src/main/java/org/pgpainless/signature/consumer/SignatureCreationDateComparator.java b/pgpainless-core/src/main/java/org/pgpainless/signature/consumer/SignatureCreationDateComparator.java
deleted file mode 100644
index 7996e33b..00000000
--- a/pgpainless-core/src/main/java/org/pgpainless/signature/consumer/SignatureCreationDateComparator.java
+++ /dev/null
@@ -1,53 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package org.pgpainless.signature.consumer;
-
-import java.util.Comparator;
-
-import org.bouncycastle.openpgp.PGPSignature;
-
-/**
- * Comparator which can be used to sort signatures with regard to their creation time.
- */
-public class SignatureCreationDateComparator implements Comparator<PGPSignature> {
-
-    public static final Order DEFAULT_ORDER = Order.OLD_TO_NEW;
-
-    public enum Order {
-        /**
-         * Oldest signatures first.
-         */
-        OLD_TO_NEW,
-
-        /**
-         * Newest signatures first.
-         */
-        NEW_TO_OLD
-    }
-
-    private final Order order;
-
-    /**
-     * Create a new comparator which sorts signatures old to new.
-     */
-    public SignatureCreationDateComparator() {
-        this(DEFAULT_ORDER);
-    }
-
-    /**
-     * Create a new comparator which sorts signatures according to the passed ordering.
-     * @param order ordering
-     */
-    public SignatureCreationDateComparator(Order order) {
-        this.order = order;
-    }
-
-    @Override
-    public int compare(PGPSignature one, PGPSignature two) {
-        return order == Order.OLD_TO_NEW
-                ? one.getCreationTime().compareTo(two.getCreationTime())
-                : two.getCreationTime().compareTo(one.getCreationTime());
-    }
-}
diff --git a/pgpainless-core/src/main/java/org/pgpainless/signature/consumer/SignatureValidityComparator.java b/pgpainless-core/src/main/java/org/pgpainless/signature/consumer/SignatureValidityComparator.java
deleted file mode 100644
index 94ebd5b2..00000000
--- a/pgpainless-core/src/main/java/org/pgpainless/signature/consumer/SignatureValidityComparator.java
+++ /dev/null
@@ -1,53 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package org.pgpainless.signature.consumer;
-
-import java.util.Comparator;
-
-import org.bouncycastle.openpgp.PGPSignature;
-import org.pgpainless.signature.SignatureUtils;
-
-/**
- * Comparator which sorts signatures based on an ordering and on revocation hardness.
- *
- * If a list of signatures gets ordered using this comparator, hard revocations will always
- * come first.
- * Further, signatures are ordered by date according to the {@link SignatureCreationDateComparator.Order}.
- */
-public class SignatureValidityComparator implements Comparator<PGPSignature> {
-
-    private final SignatureCreationDateComparator creationDateComparator;
-
-    /**
-     * Create a new {@link SignatureValidityComparator} which orders signatures the oldest first.
-     * Still, hard revocations will come first.
-     */
-    public SignatureValidityComparator() {
-        this(SignatureCreationDateComparator.DEFAULT_ORDER);
-    }
-
-    /**
-     * Create a new {@link SignatureValidityComparator} which orders signatures following the passed ordering.
-     * Still, hard revocations will come first.
-     *
-     * @param order order of creation dates
-     */
-    public SignatureValidityComparator(SignatureCreationDateComparator.Order order) {
-        this.creationDateComparator = new SignatureCreationDateComparator(order);
-    }
-
-    @Override
-    public int compare(PGPSignature one, PGPSignature two) {
-        boolean oneIsHard = SignatureUtils.isHardRevocation(one);
-        boolean twoIsHard = SignatureUtils.isHardRevocation(two);
-
-        // both have same "hardness", so compare creation time
-        if (oneIsHard == twoIsHard) {
-            return creationDateComparator.compare(one, two);
-        }
-        // favor the "harder" signature
-        return oneIsHard ? -1 : 1;
-    }
-}
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/signature/consumer/SignatureCreationDateComparator.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/consumer/SignatureCreationDateComparator.kt
new file mode 100644
index 00000000..75cd274c
--- /dev/null
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/consumer/SignatureCreationDateComparator.kt
@@ -0,0 +1,34 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.signature.consumer
+
+import org.bouncycastle.openpgp.PGPSignature
+
+/**
+ * Create a new comparator which sorts signatures according to the passed ordering.
+ * @param order ordering
+ */
+class SignatureCreationDateComparator(
+        private val order: Order = Order.OLD_TO_NEW
+) : Comparator<PGPSignature> {
+
+    enum class Order {
+        /**
+         * Oldest signatures first.
+         */
+        OLD_TO_NEW,
+        /**
+         * Newest signatures first.
+         */
+        NEW_TO_OLD
+    }
+
+    override fun compare(one: PGPSignature, two: PGPSignature): Int {
+        return when(order) {
+            Order.OLD_TO_NEW -> one.creationTime.compareTo(two.creationTime)
+            Order.NEW_TO_OLD -> two.creationTime.compareTo(one.creationTime)
+        }
+    }
+}
\ No newline at end of file
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/signature/consumer/SignatureValidityComparator.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/consumer/SignatureValidityComparator.kt
new file mode 100644
index 00000000..f2b586ae
--- /dev/null
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/consumer/SignatureValidityComparator.kt
@@ -0,0 +1,31 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.signature.consumer
+
+import org.bouncycastle.extensions.isHardRevocation
+import org.bouncycastle.openpgp.PGPSignature
+
+/**
+ * Comparator which sorts signatures based on an ordering and on revocation hardness.
+ *
+ * If a list of signatures gets ordered using this comparator, hard revocations will always
+ * come first.
+ * Further, signatures are ordered by date according to the [SignatureCreationDateComparator.Order].
+ */
+class SignatureValidityComparator(
+        order: SignatureCreationDateComparator.Order = SignatureCreationDateComparator.Order.OLD_TO_NEW
+) : Comparator<PGPSignature> {
+
+    private val creationDateComparator: SignatureCreationDateComparator = SignatureCreationDateComparator(order)
+    override fun compare(one: PGPSignature, two: PGPSignature): Int {
+        return if (one.isHardRevocation == two.isHardRevocation) {
+            // Both have the same hardness, so compare creation time
+            creationDateComparator.compare(one, two)
+        }
+        // else favor the "harder" signature
+        else if (one.isHardRevocation) -1 else 1
+    }
+
+}
\ No newline at end of file