diff --git a/sop-java/src/main/java/sop/SOP.java b/sop-java/src/main/java/sop/SOP.java
deleted file mode 100644
index 1200e21..0000000
--- a/sop-java/src/main/java/sop/SOP.java
+++ /dev/null
@@ -1,177 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package sop;
-
-import sop.operation.Armor;
-import sop.operation.ChangeKeyPassword;
-import sop.operation.Dearmor;
-import sop.operation.Decrypt;
-import sop.operation.Encrypt;
-import sop.operation.ExtractCert;
-import sop.operation.GenerateKey;
-import sop.operation.InlineDetach;
-import sop.operation.InlineSign;
-import sop.operation.InlineVerify;
-import sop.operation.DetachedSign;
-import sop.operation.DetachedVerify;
-import sop.operation.ListProfiles;
-import sop.operation.RevokeKey;
-import sop.operation.Version;
-
-/**
- * Stateless OpenPGP Interface.
- * This class provides a stateless interface to various OpenPGP related operations.
- * <br>
- * Note: Subcommand objects acquired by calling any method of this interface are not intended for reuse.
- * If you for example need to generate multiple keys, make a dedicated call to {@link #generateKey()} once per
- * key generation.
- */
-public interface SOP {
-
-    /**
-     * Get information about the implementations name and version.
-     *
-     * @return version
-     */
-    Version version();
-
-    /**
-     * Generate a secret key.
-     * Customize the operation using the builder {@link GenerateKey}.
-     *
-     * @return builder instance
-     */
-    GenerateKey generateKey();
-
-    /**
-     * Extract a certificate (public key) from a secret key.
-     * Customize the operation using the builder {@link ExtractCert}.
-     *
-     * @return builder instance
-     */
-    ExtractCert extractCert();
-
-    /**
-     * Create detached signatures.
-     * Customize the operation using the builder {@link DetachedSign}.
-     * <p>
-     * If you want to sign a message inline, use {@link #inlineSign()} instead.
-     *
-     * @return builder instance
-     */
-    default DetachedSign sign() {
-        return detachedSign();
-    }
-
-    /**
-     * Create detached signatures.
-     * Customize the operation using the builder {@link DetachedSign}.
-     * <p>
-     * If you want to sign a message inline, use {@link #inlineSign()} instead.
-     *
-     * @return builder instance
-     */
-    DetachedSign detachedSign();
-
-    /**
-     * Sign a message using inline signatures.
-     * <p>
-     * If you need to create detached signatures, use {@link #detachedSign()} instead.
-     *
-     * @return builder instance
-     */
-    InlineSign inlineSign();
-
-    /**
-     * Verify detached signatures.
-     * Customize the operation using the builder {@link DetachedVerify}.
-     * <p>
-     * If you need to verify an inline-signed message, use {@link #inlineVerify()} instead.
-     *
-     * @return builder instance
-     */
-    default DetachedVerify verify() {
-        return detachedVerify();
-    }
-
-    /**
-     * Verify detached signatures.
-     * Customize the operation using the builder {@link DetachedVerify}.
-     * <p>
-     * If you need to verify an inline-signed message, use {@link #inlineVerify()} instead.
-     *
-     * @return builder instance
-     */
-    DetachedVerify detachedVerify();
-
-    /**
-     * Verify signatures of an inline-signed message.
-     * <p>
-     * If you need to verify detached signatures over a message, use {@link #detachedVerify()} instead.
-     *
-     * @return builder instance
-     */
-    InlineVerify inlineVerify();
-
-    /**
-     * Detach signatures from an inline signed message.
-     *
-     * @return builder instance
-     */
-    InlineDetach inlineDetach();
-
-    /**
-     * Encrypt a message.
-     * Customize the operation using the builder {@link Encrypt}.
-     *
-     * @return builder instance
-     */
-    Encrypt encrypt();
-
-    /**
-     * Decrypt a message.
-     * Customize the operation using the builder {@link Decrypt}.
-     *
-     * @return builder instance
-     */
-    Decrypt decrypt();
-
-    /**
-     * Convert binary OpenPGP data to ASCII.
-     * Customize the operation using the builder {@link Armor}.
-     *
-     * @return builder instance
-     */
-    Armor armor();
-
-    /**
-     * Converts ASCII armored OpenPGP data to binary.
-     * Customize the operation using the builder {@link Dearmor}.
-     *
-     * @return builder instance
-     */
-    Dearmor dearmor();
-
-    /**
-     * List supported {@link Profile Profiles} of a subcommand.
-     *
-     * @return builder instance
-     */
-    ListProfiles listProfiles();
-
-    /**
-     * Revoke one or more secret keys.
-     *
-     * @return builder instance
-     */
-    RevokeKey revokeKey();
-
-    /**
-     * Update a key's password.
-     *
-     * @return builder instance
-     */
-    ChangeKeyPassword changeKeyPassword();
-}
diff --git a/sop-java/src/main/kotlin/sop/SOP.kt b/sop-java/src/main/kotlin/sop/SOP.kt
new file mode 100644
index 0000000..e01763a
--- /dev/null
+++ b/sop-java/src/main/kotlin/sop/SOP.kt
@@ -0,0 +1,97 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop
+
+import sop.operation.Armor
+import sop.operation.ChangeKeyPassword
+import sop.operation.Dearmor
+import sop.operation.Decrypt
+import sop.operation.DetachedSign
+import sop.operation.DetachedVerify
+import sop.operation.Encrypt
+import sop.operation.ExtractCert
+import sop.operation.GenerateKey
+import sop.operation.InlineDetach
+import sop.operation.InlineSign
+import sop.operation.InlineVerify
+import sop.operation.ListProfiles
+import sop.operation.RevokeKey
+import sop.operation.Version
+
+/**
+ * Stateless OpenPGP Interface. This class provides a stateless interface to various OpenPGP related
+ * operations. Note: Subcommand objects acquired by calling any method of this interface are not
+ * intended for reuse. If you for example need to generate multiple keys, make a dedicated call to
+ * [generateKey] once per key generation.
+ */
+interface SOP {
+
+    /** Get information about the implementations name and version. */
+    fun version(): Version
+
+    /** Generate a secret key. */
+    fun generateKey(): GenerateKey
+
+    /** Extract a certificate (public key) from a secret key. */
+    fun extractCert(): ExtractCert
+
+    /**
+     * Create detached signatures. If you want to sign a message inline, use [inlineSign] instead.
+     */
+    fun sign(): DetachedSign = detachedSign()
+
+    /**
+     * Create detached signatures. If you want to sign a message inline, use [inlineSign] instead.
+     */
+    fun detachedSign(): DetachedSign
+
+    /**
+     * Sign a message using inline signatures. If you need to create detached signatures, use
+     * [detachedSign] instead.
+     */
+    fun inlineSign(): InlineSign
+
+    /**
+     * Verify detached signatures. If you need to verify an inline-signed message, use
+     * [inlineVerify] instead.
+     */
+    fun verify(): DetachedVerify = detachedVerify()
+
+    /**
+     * Verify detached signatures. If you need to verify an inline-signed message, use
+     * [inlineVerify] instead.
+     */
+    fun detachedVerify(): DetachedVerify
+
+    /**
+     * Verify signatures of an inline-signed message. If you need to verify detached signatures over
+     * a message, use [detachedVerify] instead.
+     */
+    fun inlineVerify(): InlineVerify
+
+    /** Detach signatures from an inline signed message. */
+    fun inlineDetach(): InlineDetach
+
+    /** Encrypt a message. */
+    fun encrypt(): Encrypt
+
+    /** Decrypt a message. */
+    fun decrypt(): Decrypt
+
+    /** Convert binary OpenPGP data to ASCII. */
+    fun armor(): Armor
+
+    /** Converts ASCII armored OpenPGP data to binary. */
+    fun dearmor(): Dearmor
+
+    /** List supported [Profiles][Profile] of a subcommand. */
+    fun listProfiles(): ListProfiles
+
+    /** Revoke one or more secret keys. */
+    fun revokeKey(): RevokeKey
+
+    /** Update a key's password. */
+    fun changeKeyPassword(): ChangeKeyPassword
+}