diff --git a/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/CustomPublicKeyDataDecryptorFactory.java b/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/CustomPublicKeyDataDecryptorFactory.java
deleted file mode 100644
index 91902cc7..00000000
--- a/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/CustomPublicKeyDataDecryptorFactory.java
+++ /dev/null
@@ -1,27 +0,0 @@
-// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package org.pgpainless.decryption_verification;
-
-import org.bouncycastle.openpgp.operator.PublicKeyDataDecryptorFactory;
-import org.pgpainless.key.SubkeyIdentifier;
-
-/**
- * Custom {@link PublicKeyDataDecryptorFactory} which can enable customized implementations of message decryption
- * using public keys.
- * This class can for example be used to implement message encryption using hardware tokens like smartcards or
- * TPMs.
- * @see ConsumerOptions#addCustomDecryptorFactory(CustomPublicKeyDataDecryptorFactory)
- */
-public interface CustomPublicKeyDataDecryptorFactory extends PublicKeyDataDecryptorFactory {
-
-    /**
-     * Return the {@link SubkeyIdentifier} for which this particular {@link CustomPublicKeyDataDecryptorFactory}
-     * is intended.
-     *
-     * @return subkey identifier
-     */
-    SubkeyIdentifier getSubkeyIdentifier();
-
-}
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/CustomPublicKeyDataDecryptorFactory.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/CustomPublicKeyDataDecryptorFactory.kt
new file mode 100644
index 00000000..b7f57da3
--- /dev/null
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/CustomPublicKeyDataDecryptorFactory.kt
@@ -0,0 +1,26 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.decryption_verification
+
+import org.bouncycastle.openpgp.operator.PublicKeyDataDecryptorFactory
+import org.pgpainless.key.SubkeyIdentifier
+
+/**
+ * Custom [PublicKeyDataDecryptorFactory] which can enable customized implementations of message decryption
+ * using public keys.
+ * This class can for example be used to implement message encryption using hardware tokens like smartcards or
+ * TPMs.
+ * @see [ConsumerOptions.addCustomDecryptorFactory]
+ */
+interface CustomPublicKeyDataDecryptorFactory : PublicKeyDataDecryptorFactory {
+
+    /**
+     * Identifier for the subkey for which this particular [CustomPublicKeyDataDecryptorFactory]
+     * is intended.
+     *
+     * @return subkey identifier
+     */
+    val subkeyIdentifier: SubkeyIdentifier
+}
\ No newline at end of file