diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/SubkeyIdentifier.java b/pgpainless-core/src/main/java/org/pgpainless/key/SubkeyIdentifier.java
deleted file mode 100644
index 8bfd7f7c..00000000
--- a/pgpainless-core/src/main/java/org/pgpainless/key/SubkeyIdentifier.java
+++ /dev/null
@@ -1,146 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package org.pgpainless.key;
-
-import java.util.NoSuchElementException;
-import javax.annotation.Nonnull;
-
-import org.bouncycastle.openpgp.PGPKeyRing;
-import org.bouncycastle.openpgp.PGPPublicKey;
-
-/**
- * Tuple class used to identify a subkey by fingerprints of the primary key of the subkeys key ring,
- * as well as the subkeys fingerprint.
- */
-public class SubkeyIdentifier {
-
-    private final OpenPgpFingerprint primaryKeyFingerprint;
-    private final OpenPgpFingerprint subkeyFingerprint;
-
-    /**
-     * Create a {@link SubkeyIdentifier} from a {@link PGPKeyRing}.
-     * The identifier will point to the primary key of the provided ring.
-     *
-     * @param keyRing key ring
-     */
-    public SubkeyIdentifier(PGPKeyRing keyRing) {
-        this(keyRing, keyRing.getPublicKey().getKeyID());
-    }
-
-    /**
-     * Create a {@link SubkeyIdentifier} from a {@link PGPKeyRing} and the subkeys key id.
-     * {@link #getPrimaryKeyFingerprint()} will return the {@link OpenPgpFingerprint} of the keyrings primary key,
-     * while {@link #getSubkeyFingerprint()} will return the subkeys fingerprint.
-     *
-     * @param keyRing keyring the subkey belongs to
-     * @param keyId keyid of the subkey
-     */
-    public SubkeyIdentifier(@Nonnull PGPKeyRing keyRing, long keyId) {
-        PGPPublicKey subkey = keyRing.getPublicKey(keyId);
-        if (subkey == null) {
-            throw new NoSuchElementException("Key ring does not contain subkey with id " + Long.toHexString(keyId));
-        }
-        this.primaryKeyFingerprint = OpenPgpFingerprint.of(keyRing);
-        this.subkeyFingerprint = OpenPgpFingerprint.of(subkey);
-    }
-
-    public SubkeyIdentifier(@Nonnull PGPKeyRing keyRing, @Nonnull OpenPgpFingerprint subkeyFingerprint) {
-        this(OpenPgpFingerprint.of(keyRing), subkeyFingerprint);
-    }
-
-    /**
-     * Create a {@link SubkeyIdentifier} that identifies the primary key with the given fingerprint.
-     * This means, both {@link #getPrimaryKeyFingerprint()} and {@link #getSubkeyFingerprint()} return the same.
-     *
-     * @param primaryKeyFingerprint fingerprint of the identified key
-     */
-    public SubkeyIdentifier(@Nonnull OpenPgpFingerprint primaryKeyFingerprint) {
-        this(primaryKeyFingerprint, primaryKeyFingerprint);
-    }
-
-    /**
-     * Create a {@link SubkeyIdentifier} which points to the subkey with the given subkeyFingerprint,
-     * which has a primary key with the given primaryKeyFingerprint.
-     *
-     * @param primaryKeyFingerprint fingerprint of the primary key
-     * @param subkeyFingerprint fingerprint of the subkey
-     */
-    public SubkeyIdentifier(@Nonnull OpenPgpFingerprint primaryKeyFingerprint, @Nonnull OpenPgpFingerprint subkeyFingerprint) {
-        this.primaryKeyFingerprint = primaryKeyFingerprint;
-        this.subkeyFingerprint = subkeyFingerprint;
-    }
-
-    public @Nonnull OpenPgpFingerprint getFingerprint() {
-        return getSubkeyFingerprint();
-    }
-
-    public long getKeyId() {
-        return getSubkeyId();
-    }
-
-    /**
-     * Return the {@link OpenPgpFingerprint} of the primary key of the identified key.
-     * This might be the same as {@link #getSubkeyFingerprint()} if the identified subkey is the primary key.
-     *
-     * @return primary key fingerprint
-     */
-    public @Nonnull OpenPgpFingerprint getPrimaryKeyFingerprint() {
-        return primaryKeyFingerprint;
-    }
-
-    /**
-     * Return the key id of the primary key of the identified key.
-     * This might be the same as {@link #getSubkeyId()} if the identified subkey is the primary key.
-     *
-     * @return primary key id
-     */
-    public long getPrimaryKeyId() {
-        return getPrimaryKeyFingerprint().getKeyId();
-    }
-
-    /**
-     * Return the {@link OpenPgpFingerprint} of the identified subkey.
-     *
-     * @return subkey fingerprint
-     */
-    public @Nonnull OpenPgpFingerprint getSubkeyFingerprint() {
-        return subkeyFingerprint;
-    }
-
-    /**
-     * Return the key id of the identified subkey.
-     *
-     * @return subkey id
-     */
-    public long getSubkeyId() {
-        return getSubkeyFingerprint().getKeyId();
-    }
-
-    @Override
-    public int hashCode() {
-        return primaryKeyFingerprint.hashCode() * 31 + subkeyFingerprint.hashCode();
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        if (obj == null) {
-            return false;
-        }
-        if (this == obj) {
-            return true;
-        }
-        if (!(obj instanceof SubkeyIdentifier)) {
-            return false;
-        }
-        SubkeyIdentifier other = (SubkeyIdentifier) obj;
-        return getPrimaryKeyFingerprint().equals(other.getPrimaryKeyFingerprint())
-                && getSubkeyFingerprint().equals(other.getSubkeyFingerprint());
-    }
-
-    @Override
-    public String toString() {
-        return getSubkeyFingerprint() + " " + getPrimaryKeyFingerprint();
-    }
-}
diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/SubkeyIdentifier.kt b/pgpainless-core/src/main/java/org/pgpainless/key/SubkeyIdentifier.kt
new file mode 100644
index 00000000..61b45874
--- /dev/null
+++ b/pgpainless-core/src/main/java/org/pgpainless/key/SubkeyIdentifier.kt
@@ -0,0 +1,53 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.key
+
+import org.bouncycastle.openpgp.PGPKeyRing
+import org.bouncycastle.openpgp.PGPPublicKey
+import org.pgpainless.key.util.KeyIdUtil
+
+/**
+ * Tuple class used to identify a subkey by fingerprints of the primary key of the subkeys key ring,
+ * as well as the subkeys fingerprint.
+ */
+class SubkeyIdentifier(
+        val primaryKeyFingerprint: OpenPgpFingerprint,
+        val subkeyFingerprint: OpenPgpFingerprint) {
+
+    constructor(fingerprint: OpenPgpFingerprint): this(fingerprint, fingerprint)
+    constructor(keys: PGPKeyRing): this(keys.publicKey)
+    constructor(key: PGPPublicKey): this(OpenPgpFingerprint.of(key))
+    constructor(keys: PGPKeyRing, keyId: Long): this(
+                    OpenPgpFingerprint.of(keys.publicKey),
+                    OpenPgpFingerprint.of(keys.getPublicKey(keyId) ?:
+                    throw NoSuchElementException("OpenPGP key does not contain subkey ${KeyIdUtil.formatKeyId(keyId)}")))
+    constructor(keys: PGPKeyRing, subkeyFingerprint: OpenPgpFingerprint): this(OpenPgpFingerprint.of(keys), subkeyFingerprint)
+
+    val keyId = subkeyFingerprint.keyId
+    val fingerprint = subkeyFingerprint
+
+    val subkeyId = subkeyFingerprint.keyId
+    val primaryKeyId = primaryKeyFingerprint.keyId
+
+    override fun equals(other: Any?): Boolean {
+        if (other == null) {
+            return false
+        }
+        if (this === other) {
+            return true
+        }
+        if (other !is SubkeyIdentifier) {
+            return false
+        }
+
+        return primaryKeyFingerprint.equals(other.primaryKeyFingerprint) && subkeyFingerprint.equals(other.subkeyFingerprint)
+    }
+
+    override fun hashCode(): Int {
+        return primaryKeyFingerprint.hashCode() + 31 * subkeyFingerprint.hashCode()
+    }
+
+    override fun toString(): String = "$subkeyFingerprint $primaryKeyFingerprint"
+}
\ No newline at end of file