diff --git a/pgpainless-core/src/main/java/org/pgpainless/encryption_signing/SignatureGenerationStream.java b/pgpainless-core/src/main/java/org/pgpainless/encryption_signing/SignatureGenerationStream.java
deleted file mode 100644
index 7a96f2e1..00000000
--- a/pgpainless-core/src/main/java/org/pgpainless/encryption_signing/SignatureGenerationStream.java
+++ /dev/null
@@ -1,65 +0,0 @@
-// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package org.pgpainless.encryption_signing;
-
-import org.bouncycastle.openpgp.PGPSignatureGenerator;
-import org.pgpainless.key.SubkeyIdentifier;
-
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-import java.io.IOException;
-import java.io.OutputStream;
-
-/**
- * OutputStream which has the task of updating signature generators for written data.
- */
-class SignatureGenerationStream extends OutputStream {
-
-    private final OutputStream wrapped;
-    private final SigningOptions options;
-
-    SignatureGenerationStream(@Nonnull OutputStream wrapped, @Nullable SigningOptions signingOptions) {
-        this.wrapped = wrapped;
-        this.options = signingOptions;
-    }
-
-    @Override
-    public void write(int b) throws IOException {
-        wrapped.write(b);
-        if (options == null || options.getSigningMethods().isEmpty()) {
-            return;
-        }
-
-        for (SubkeyIdentifier signingKey : options.getSigningMethods().keySet()) {
-            SigningOptions.SigningMethod signingMethod = options.getSigningMethods().get(signingKey);
-            PGPSignatureGenerator signatureGenerator = signingMethod.getSignatureGenerator();
-            byte asByte = (byte) (b & 0xff);
-            signatureGenerator.update(asByte);
-        }
-    }
-
-    @Override
-    public void write(@Nonnull byte[] buffer) throws IOException {
-        write(buffer, 0, buffer.length);
-    }
-
-    @Override
-    public void write(@Nonnull byte[] buffer, int off, int len) throws IOException {
-        wrapped.write(buffer, 0, len);
-        if (options == null || options.getSigningMethods().isEmpty()) {
-            return;
-        }
-        for (SubkeyIdentifier signingKey : options.getSigningMethods().keySet()) {
-            SigningOptions.SigningMethod signingMethod = options.getSigningMethods().get(signingKey);
-            PGPSignatureGenerator signatureGenerator = signingMethod.getSignatureGenerator();
-            signatureGenerator.update(buffer, 0, len);
-        }
-    }
-
-    @Override
-    public void close() throws IOException {
-        wrapped.close();
-    }
-}
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/encryption_signing/SignatureGenerationStream.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/encryption_signing/SignatureGenerationStream.kt
new file mode 100644
index 00000000..d0f04851
--- /dev/null
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/encryption_signing/SignatureGenerationStream.kt
@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.encryption_signing
+
+import java.io.OutputStream
+
+/**
+ * OutputStream which has the task of updating signature generators for written data.
+ */
+class SignatureGenerationStream(
+        private val wrapped: OutputStream,
+        private val options: SigningOptions?
+) : OutputStream() {
+
+    override fun close() = wrapped.close()
+    override fun flush() = wrapped.flush()
+
+    override fun write(b: Int) {
+        wrapped.write(b)
+        options?.run {
+            signingMethods.values.forEach {
+                it.signatureGenerator.update((b and 0xff).toByte())
+            }
+        }
+    }
+
+    override fun write(b: ByteArray) = write(b, 0, b.size)
+
+    override fun write(b: ByteArray, off: Int, len: Int) {
+        wrapped.write(b, off, len)
+        options?.run {
+            signingMethods.values.forEach {
+                it.signatureGenerator.update(b, off, len)
+            }
+        }
+    }
+}
\ No newline at end of file