diff --git a/sop-java/src/main/java/sop/operation/GenerateKey.java b/sop-java/src/main/java/sop/operation/GenerateKey.java
deleted file mode 100644
index 77afea1..0000000
--- a/sop-java/src/main/java/sop/operation/GenerateKey.java
+++ /dev/null
@@ -1,103 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package sop.operation;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.nio.charset.CharacterCodingException;
-
-import sop.Profile;
-import sop.Ready;
-import sop.exception.SOPGPException;
-import sop.util.UTF8Util;
-
-public interface GenerateKey {
-
-    /**
-     * Disable ASCII armor encoding.
-     *
-     * @return builder instance
-     */
-    GenerateKey noArmor();
-
-    /**
-     * Adds a user-id.
-     *
-     * @param userId user-id
-     * @return builder instance
-     */
-    GenerateKey userId(String userId);
-
-    /**
-     * Set a password for the key.
-     *
-     * @param password password to protect the key
-     * @return builder instance
-     *
-     * @throws sop.exception.SOPGPException.UnsupportedOption if key passwords are not supported
-     * @throws sop.exception.SOPGPException.PasswordNotHumanReadable if the password is not human-readable
-     */
-    GenerateKey withKeyPassword(String password)
-            throws SOPGPException.PasswordNotHumanReadable,
-            SOPGPException.UnsupportedOption;
-
-    /**
-     * Set a password for the key.
-     *
-     * @param password password to protect the key
-     * @return builder instance
-     *
-     * @throws sop.exception.SOPGPException.PasswordNotHumanReadable if the password is not human-readable
-     * @throws sop.exception.SOPGPException.UnsupportedOption if key passwords are not supported
-     */
-    default GenerateKey withKeyPassword(byte[] password)
-            throws SOPGPException.PasswordNotHumanReadable,
-            SOPGPException.UnsupportedOption {
-        try {
-            return withKeyPassword(UTF8Util.decodeUTF8(password));
-        } catch (CharacterCodingException e) {
-            throw new SOPGPException.PasswordNotHumanReadable();
-        }
-    }
-
-    /**
-     * Pass in a profile.
-     *
-     * @param profile profile
-     * @return builder instance
-     */
-    default GenerateKey profile(Profile profile) {
-        return profile(profile.getName());
-    }
-
-    /**
-     * Pass in a profile identifier.
-     *
-     * @param profile profile identifier
-     * @return builder instance
-     */
-    GenerateKey profile(String profile);
-
-    /**
-     * If this options is set, the generated key will not be capable of encryption / decryption.
-     *
-     * @return builder instance
-     */
-    GenerateKey signingOnly();
-
-    /**
-     * Generate the OpenPGP key and return it encoded as an {@link InputStream}.
-     *
-     * @return key
-     *
-     * @throws sop.exception.SOPGPException.MissingArg if no user-id was provided
-     * @throws sop.exception.SOPGPException.UnsupportedAsymmetricAlgo if the generated key uses an unsupported asymmetric algorithm
-     * @throws IOException in case of an IO error
-     */
-    Ready generate()
-            throws SOPGPException.MissingArg,
-            SOPGPException.UnsupportedAsymmetricAlgo,
-            IOException;
-}
diff --git a/sop-java/src/main/kotlin/sop/operation/GenerateKey.kt b/sop-java/src/main/kotlin/sop/operation/GenerateKey.kt
new file mode 100644
index 0000000..3b83b99
--- /dev/null
+++ b/sop-java/src/main/kotlin/sop/operation/GenerateKey.kt
@@ -0,0 +1,91 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop.operation
+
+import java.io.IOException
+import sop.Profile
+import sop.Ready
+import sop.exception.SOPGPException.*
+import sop.util.UTF8Util
+
+interface GenerateKey {
+
+    /**
+     * Disable ASCII armor encoding.
+     *
+     * @return builder instance
+     */
+    fun noArmor(): GenerateKey
+
+    /**
+     * Adds a user-id.
+     *
+     * @param userId user-id
+     * @return builder instance
+     */
+    fun userId(userId: String): GenerateKey
+
+    /**
+     * Set a password for the key.
+     *
+     * @param password password to protect the key
+     * @return builder instance
+     * @throws UnsupportedOption if key passwords are not supported
+     * @throws PasswordNotHumanReadable if the password is not human-readable
+     */
+    @Throws(PasswordNotHumanReadable::class, UnsupportedOption::class)
+    fun withKeyPassword(password: String): GenerateKey
+
+    /**
+     * Set a password for the key.
+     *
+     * @param password password to protect the key
+     * @return builder instance
+     * @throws PasswordNotHumanReadable if the password is not human-readable
+     * @throws UnsupportedOption if key passwords are not supported
+     */
+    @Throws(PasswordNotHumanReadable::class, UnsupportedOption::class)
+    fun withKeyPassword(password: ByteArray): GenerateKey =
+        try {
+            withKeyPassword(UTF8Util.decodeUTF8(password))
+        } catch (e: CharacterCodingException) {
+            throw PasswordNotHumanReadable()
+        }
+
+    /**
+     * Pass in a profile.
+     *
+     * @param profile profile
+     * @return builder instance
+     */
+    fun profile(profile: Profile): GenerateKey = profile(profile.name)
+
+    /**
+     * Pass in a profile identifier.
+     *
+     * @param profile profile identifier
+     * @return builder instance
+     */
+    fun profile(profile: String): GenerateKey
+
+    /**
+     * If this options is set, the generated key will not be capable of encryption / decryption.
+     *
+     * @return builder instance
+     */
+    fun signingOnly(): GenerateKey
+
+    /**
+     * Generate the OpenPGP key and return it encoded as an [InputStream].
+     *
+     * @return key
+     * @throws MissingArg if no user-id was provided
+     * @throws UnsupportedAsymmetricAlgo if the generated key uses an unsupported asymmetric
+     *   algorithm
+     * @throws IOException in case of an IO error
+     */
+    @Throws(MissingArg::class, UnsupportedAsymmetricAlgo::class, IOException::class)
+    fun generate(): Ready
+}