diff --git a/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/DecryptionBuilder.java b/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/DecryptionBuilder.java
index da4c2a14..4b063eae 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/DecryptionBuilder.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/DecryptionBuilder.java
@@ -15,13 +15,12 @@
  */
 package org.pgpainless.decryption_verification;
 
-import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Set;
-import java.util.function.Predicate;
+import javax.annotation.Nonnull;
 
 import org.bouncycastle.openpgp.PGPException;
 import org.bouncycastle.openpgp.PGPPublicKeyRing;
diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/OpenPgpV4Fingerprint.java b/pgpainless-core/src/main/java/org/pgpainless/key/OpenPgpV4Fingerprint.java
index 9bceee8a..a7d34b84 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/key/OpenPgpV4Fingerprint.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/key/OpenPgpV4Fingerprint.java
@@ -15,10 +15,9 @@
  */
 package org.pgpainless.key;
 
-import javax.annotation.Nonnull;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
-import java.nio.charset.StandardCharsets;
+import javax.annotation.Nonnull;
 
 import org.bouncycastle.openpgp.PGPPublicKey;
 import org.bouncycastle.openpgp.PGPPublicKeyRing;
diff --git a/pgpainless-core/src/main/java/org/pgpainless/provider/BouncyCastleProviderFactory.java b/pgpainless-core/src/main/java/org/pgpainless/provider/BouncyCastleProviderFactory.java
index 32e7aaa2..c4aa3d1d 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/provider/BouncyCastleProviderFactory.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/provider/BouncyCastleProviderFactory.java
@@ -1,3 +1,18 @@
+/*
+ * Copyright 2020 Paul Schaub.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package org.pgpainless.provider;
 
 import java.security.Provider;
diff --git a/pgpainless-core/src/main/java/org/pgpainless/provider/ProviderFactory.java b/pgpainless-core/src/main/java/org/pgpainless/provider/ProviderFactory.java
index 9030fe46..f24f30c0 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/provider/ProviderFactory.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/provider/ProviderFactory.java
@@ -1,3 +1,18 @@
+/*
+ * Copyright 2020 Paul Schaub.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package org.pgpainless.provider;
 
 import java.security.Provider;
diff --git a/pgpainless-core/src/main/java/org/pgpainless/provider/package-info.java b/pgpainless-core/src/main/java/org/pgpainless/provider/package-info.java
new file mode 100644
index 00000000..92c3cc32
--- /dev/null
+++ b/pgpainless-core/src/main/java/org/pgpainless/provider/package-info.java
@@ -0,0 +1,19 @@
+/*
+ * Copyright 2020 Paul Schaub.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/**
+ * Classes that allow setting a custom implementation of {@link java.security.Provider}.
+ */
+package org.pgpainless.provider;
diff --git a/pgpainless-core/src/test/java/org/pgpainless/ProviderFactoryTest.java b/pgpainless-core/src/test/java/org/pgpainless/ProviderFactoryTest.java
index f694d131..08a8dae3 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/ProviderFactoryTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/ProviderFactoryTest.java
@@ -1,3 +1,18 @@
+/*
+ * Copyright 2020 Paul Schaub.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package org.pgpainless;
 
 import static junit.framework.TestCase.assertEquals;