diff --git a/pgpainless-core/src/test/java/org/pgpainless/algorithm/KeyFlagTest.java b/pgpainless-core/src/test/java/org/pgpainless/algorithm/KeyFlagTest.java
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+++ b/pgpainless-core/src/test/java/org/pgpainless/algorithm/KeyFlagTest.java
@@ -0,0 +1,97 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.algorithm;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+public class KeyFlagTest {
+
+    @Test
+    public void testEmptyBitmaskHasNoFlags() {
+        int bitmask = KeyFlag.toBitmask();
+        assertEquals(0, bitmask);
+        for (KeyFlag flag : KeyFlag.values()) {
+            assertFalse(KeyFlag.hasKeyFlag(bitmask, flag));
+        }
+    }
+
+    @Test
+    public void testEmptyBitmaskToKeyFlags() {
+        int emptyMask = 0;
+        List<KeyFlag> flags = KeyFlag.fromBitmask(emptyMask);
+        assertTrue(flags.isEmpty());
+    }
+
+    @Test
+    public void testSingleBitmaskToKeyFlags() {
+        for (KeyFlag flag : KeyFlag.values()) {
+            int singleMask = KeyFlag.toBitmask(flag);
+            List<KeyFlag> singletonList = KeyFlag.fromBitmask(singleMask);
+            assertEquals(1, singletonList.size());
+            assertEquals(flag, singletonList.get(0));
+        }
+    }
+
+    @Test
+    public void testKeyFlagsToBitmaskToList() {
+        int bitMask = KeyFlag.toBitmask(KeyFlag.ENCRYPT_COMMS, KeyFlag.ENCRYPT_STORAGE);
+        List<KeyFlag> flags = KeyFlag.fromBitmask(bitMask);
+
+        assertEquals(2, flags.size());
+        assertTrue(flags.contains(KeyFlag.ENCRYPT_COMMS));
+        assertTrue(flags.contains(KeyFlag.ENCRYPT_STORAGE));
+    }
+
+    @Test
+    public void testSingleKeyFlagToBitmask() {
+        for (KeyFlag flag : KeyFlag.values()) {
+            int bitmask = KeyFlag.toBitmask(flag);
+            assertEquals(flag.getFlag(), bitmask);
+        }
+    }
+
+    @Test
+    public void testDuplicateFlagsDoNotChangeMask() {
+        int mask = KeyFlag.toBitmask(KeyFlag.ENCRYPT_STORAGE, KeyFlag.ENCRYPT_COMMS, KeyFlag.ENCRYPT_COMMS);
+        assertEquals(KeyFlag.toBitmask(KeyFlag.ENCRYPT_COMMS, KeyFlag.ENCRYPT_STORAGE), mask);
+    }
+
+    @Test
+    public void testMaskHasNot() {
+        int mask = KeyFlag.toBitmask(KeyFlag.ENCRYPT_STORAGE);
+        assertFalse(KeyFlag.hasKeyFlag(mask, KeyFlag.ENCRYPT_COMMS));
+    }
+
+    @Test
+    public void testMaskContainsNone() {
+        int mask = KeyFlag.toBitmask(KeyFlag.ENCRYPT_COMMS, KeyFlag.ENCRYPT_STORAGE);
+
+        assertFalse(KeyFlag.containsAny(mask, KeyFlag.SIGN_DATA, KeyFlag.CERTIFY_OTHER));
+    }
+
+    @Test
+    public void testContainsAnyContainsAllExact() {
+        int mask = KeyFlag.toBitmask(KeyFlag.ENCRYPT_STORAGE, KeyFlag.ENCRYPT_COMMS);
+        assertTrue(KeyFlag.containsAny(mask, KeyFlag.ENCRYPT_STORAGE, KeyFlag.ENCRYPT_COMMS));
+    }
+
+    @Test
+    public void testContainsAnyContainsAll() {
+        int mask = KeyFlag.toBitmask(KeyFlag.CERTIFY_OTHER, KeyFlag.SIGN_DATA, KeyFlag.AUTHENTICATION);
+        assertTrue(KeyFlag.containsAny(mask, KeyFlag.SIGN_DATA, KeyFlag.AUTHENTICATION));
+    }
+
+    @Test
+    public void testContainsAnyContainsSome() {
+        int mask = KeyFlag.toBitmask(KeyFlag.CERTIFY_OTHER, KeyFlag.SIGN_DATA, KeyFlag.AUTHENTICATION);
+        assertTrue(KeyFlag.containsAny(mask, KeyFlag.CERTIFY_OTHER));
+    }
+}