diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/CachingSecretKeyRingProtector.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/CachingSecretKeyRingProtector.kt
index 5a3ff47f..20704685 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/CachingSecretKeyRingProtector.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/CachingSecretKeyRingProtector.kt
@@ -21,7 +21,7 @@ import org.pgpainless.util.Passphrase
  */
 class CachingSecretKeyRingProtector : SecretKeyRingProtector, SecretKeyPassphraseProvider {
 
-    private val cache: MutableMap<Long, Passphrase>
+    private val cache: MutableMap<Long?, Passphrase>
     private val protector: SecretKeyRingProtector
     private val provider: SecretKeyPassphraseProvider?
 
@@ -152,12 +152,12 @@ class CachingSecretKeyRingProtector : SecretKeyRingProtector, SecretKeyPassphras
      */
     fun forgetPassphrase(key: PGPPublicKey) = apply { forgetPassphrase(key.keyID) }
 
-    override fun getPassphraseFor(keyId: Long): Passphrase? {
+    override fun getPassphraseFor(keyId: Long?): Passphrase? {
         return if (hasPassphrase(keyId)) cache[keyId]
         else provider?.getPassphraseFor(keyId)?.also { cache[keyId] = it }
     }
 
-    override fun hasPassphrase(keyId: Long) = cache[keyId]?.isValid ?: false
+    override fun hasPassphrase(keyId: Long?) = cache[keyId]?.isValid ?: false
 
     override fun hasPassphraseFor(keyId: Long) = hasPassphrase(keyId)
 
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/PasswordBasedSecretKeyRingProtector.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/PasswordBasedSecretKeyRingProtector.kt
index 74ef881f..9eb47e88 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/PasswordBasedSecretKeyRingProtector.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/PasswordBasedSecretKeyRingProtector.kt
@@ -38,12 +38,12 @@ class PasswordBasedSecretKeyRingProtector : BaseSecretKeyRingProtector {
         ): PasswordBasedSecretKeyRingProtector {
             return object : SecretKeyPassphraseProvider {
 
-                    override fun getPassphraseFor(keyId: Long): Passphrase? {
+                    override fun getPassphraseFor(keyId: Long?): Passphrase? {
                         return if (hasPassphrase(keyId)) passphrase else null
                     }
 
-                    override fun hasPassphrase(keyId: Long): Boolean {
-                        return keyRing.getPublicKey(keyId) != null
+                    override fun hasPassphrase(keyId: Long?): Boolean {
+                        return keyId != null && keyRing.getPublicKey(keyId) != null
                     }
                 }
                 .let { PasswordBasedSecretKeyRingProtector(it) }
@@ -59,11 +59,11 @@ class PasswordBasedSecretKeyRingProtector : BaseSecretKeyRingProtector {
             passphrase: Passphrase
         ): PasswordBasedSecretKeyRingProtector {
             return object : SecretKeyPassphraseProvider {
-                    override fun getPassphraseFor(keyId: Long): Passphrase? {
+                    override fun getPassphraseFor(keyId: Long?): Passphrase? {
                         return if (hasPassphrase(keyId)) passphrase else null
                     }
 
-                    override fun hasPassphrase(keyId: Long): Boolean {
+                    override fun hasPassphrase(keyId: Long?): Boolean {
                         return keyId == singleKeyId
                     }
                 }
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/MapBasedPassphraseProvider.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/MapBasedPassphraseProvider.kt
index ffa3619a..3457cff7 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/MapBasedPassphraseProvider.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/MapBasedPassphraseProvider.kt
@@ -14,9 +14,9 @@ import org.pgpainless.util.Passphrase
  *
  * TODO: Make this null-safe and throw an exception instead?
  */
-class MapBasedPassphraseProvider(val map: Map<Long, Passphrase>) : SecretKeyPassphraseProvider {
+class MapBasedPassphraseProvider(val map: Map<Long?, Passphrase>) : SecretKeyPassphraseProvider {
 
-    override fun getPassphraseFor(keyId: Long): Passphrase? = map[keyId]
+    override fun getPassphraseFor(keyId: Long?): Passphrase? = map[keyId]
 
-    override fun hasPassphrase(keyId: Long): Boolean = map.containsKey(keyId)
+    override fun hasPassphrase(keyId: Long?): Boolean = map.containsKey(keyId)
 }
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SecretKeyPassphraseProvider.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SecretKeyPassphraseProvider.kt
index d872da51..a80b8bb0 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SecretKeyPassphraseProvider.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SecretKeyPassphraseProvider.kt
@@ -30,7 +30,7 @@ interface SecretKeyPassphraseProvider {
      * @param keyId if of the secret key
      * @return passphrase or null, if no passphrase record has been found.
      */
-    fun getPassphraseFor(keyId: Long): Passphrase?
+    fun getPassphraseFor(keyId: Long?): Passphrase?
 
-    fun hasPassphrase(keyId: Long): Boolean
+    fun hasPassphrase(keyId: Long?): Boolean
 }
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SolitaryPassphraseProvider.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SolitaryPassphraseProvider.kt
index a8a1735d..a9f6801d 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SolitaryPassphraseProvider.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/passphrase_provider/SolitaryPassphraseProvider.kt
@@ -9,7 +9,7 @@ import org.pgpainless.util.Passphrase
 /** Implementation of the [SecretKeyPassphraseProvider] that holds a single [Passphrase]. */
 class SolitaryPassphraseProvider(val passphrase: Passphrase?) : SecretKeyPassphraseProvider {
 
-    override fun getPassphraseFor(keyId: Long): Passphrase? = passphrase
+    override fun getPassphraseFor(keyId: Long?): Passphrase? = passphrase
 
-    override fun hasPassphrase(keyId: Long): Boolean = true
+    override fun hasPassphrase(keyId: Long?): Boolean = true
 }
diff --git a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/MissingPassphraseForDecryptionTest.java b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/MissingPassphraseForDecryptionTest.java
index 1cf55a4d..42562713 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/MissingPassphraseForDecryptionTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/MissingPassphraseForDecryptionTest.java
@@ -63,13 +63,13 @@ public class MissingPassphraseForDecryptionTest {
         // interactive callback
         SecretKeyPassphraseProvider callback = new SecretKeyPassphraseProvider() {
             @Override
-            public Passphrase getPassphraseFor(long keyId) {
+            public Passphrase getPassphraseFor(Long keyId) {
                 // is called in interactive mode
                 return Passphrase.fromPassword(passphrase);
             }
 
             @Override
-            public boolean hasPassphrase(long keyId) {
+            public boolean hasPassphrase(Long keyId) {
                 return true;
             }
         };
@@ -95,13 +95,13 @@ public class MissingPassphraseForDecryptionTest {
 
         SecretKeyPassphraseProvider callback = new SecretKeyPassphraseProvider() {
             @Override
-            public Passphrase getPassphraseFor(long keyId) {
+            public Passphrase getPassphraseFor(Long keyId) {
                 fail("MUST NOT get called in non-interactive mode.");
                 return null;
             }
 
             @Override
-            public boolean hasPassphrase(long keyId) {
+            public boolean hasPassphrase(Long keyId) {
                 return true;
             }
         };
diff --git a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/PostponeDecryptionUsingKeyWithMissingPassphraseTest.java b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/PostponeDecryptionUsingKeyWithMissingPassphraseTest.java
index 914f477e..c86a823c 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/PostponeDecryptionUsingKeyWithMissingPassphraseTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/PostponeDecryptionUsingKeyWithMissingPassphraseTest.java
@@ -120,13 +120,13 @@ public class PostponeDecryptionUsingKeyWithMissingPassphraseTest {
     public void missingPassphraseFirst() throws PGPException, IOException {
         SecretKeyRingProtector protector1 = new CachingSecretKeyRingProtector(new SecretKeyPassphraseProvider() {
             @Override
-            public Passphrase getPassphraseFor(long keyId) {
+            public Passphrase getPassphraseFor(Long keyId) {
                 fail("Although the first PKESK is for k1, we should have skipped it and tried k2 first, which has passphrase available.");
                 return null;
             }
 
             @Override
-            public boolean hasPassphrase(long keyId) {
+            public boolean hasPassphrase(Long keyId) {
                 return false;
             }
         });
@@ -150,13 +150,13 @@ public class PostponeDecryptionUsingKeyWithMissingPassphraseTest {
         SecretKeyRingProtector protector1 = SecretKeyRingProtector.unlockEachKeyWith(p1, k1);
         SecretKeyRingProtector protector2 = new CachingSecretKeyRingProtector(new SecretKeyPassphraseProvider() {
             @Override
-            public Passphrase getPassphraseFor(long keyId) {
+            public Passphrase getPassphraseFor(Long keyId) {
                 fail("This callback should not get called, since the first PKESK is for k1, which has a passphrase available.");
                 return null;
             }
 
             @Override
-            public boolean hasPassphrase(long keyId) {
+            public boolean hasPassphrase(Long keyId) {
                 return false;
             }
         });
@@ -178,13 +178,13 @@ public class PostponeDecryptionUsingKeyWithMissingPassphraseTest {
     public void messagePassphraseFirst() throws PGPException, IOException {
         SecretKeyPassphraseProvider provider = new SecretKeyPassphraseProvider() {
             @Override
-            public Passphrase getPassphraseFor(long keyId) {
+            public Passphrase getPassphraseFor(Long keyId) {
                 fail("Since we provide a decryption passphrase, we should not try to decrypt any key.");
                 return null;
             }
 
             @Override
-            public boolean hasPassphrase(long keyId) {
+            public boolean hasPassphrase(Long keyId) {
                 return false;
             }
         };
diff --git a/pgpainless-core/src/test/java/org/pgpainless/key/protection/CachingSecretKeyRingProtectorTest.java b/pgpainless-core/src/test/java/org/pgpainless/key/protection/CachingSecretKeyRingProtectorTest.java
index 9869f7b5..3f7a9e6e 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/key/protection/CachingSecretKeyRingProtectorTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/key/protection/CachingSecretKeyRingProtectorTest.java
@@ -32,13 +32,13 @@ public class CachingSecretKeyRingProtectorTest {
     // Dummy passphrase callback that returns the doubled key-id as passphrase
     private final SecretKeyPassphraseProvider dummyCallback = new SecretKeyPassphraseProvider() {
         @Override
-        public Passphrase getPassphraseFor(long keyId) {
+        public Passphrase getPassphraseFor(Long keyId) {
             long doubled = keyId * 2;
             return Passphrase.fromPassword(Long.toString(doubled));
         }
 
         @Override
-        public boolean hasPassphrase(long keyId) {
+        public boolean hasPassphrase(Long keyId) {
             return true;
         }
     };
diff --git a/pgpainless-core/src/test/java/org/pgpainless/key/protection/PassphraseProtectedKeyTest.java b/pgpainless-core/src/test/java/org/pgpainless/key/protection/PassphraseProtectedKeyTest.java
index b5703eef..370cfd85 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/key/protection/PassphraseProtectedKeyTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/key/protection/PassphraseProtectedKeyTest.java
@@ -31,7 +31,7 @@ public class PassphraseProtectedKeyTest {
             new SecretKeyPassphraseProvider() {
                 @Nullable
                 @Override
-                public Passphrase getPassphraseFor(long keyId) {
+                public Passphrase getPassphraseFor(Long keyId) {
                     if (keyId == TestKeys.CRYPTIE_KEY_ID) {
                         return new Passphrase(TestKeys.CRYPTIE_PASSWORD.toCharArray());
                     } else {
@@ -40,7 +40,7 @@ public class PassphraseProtectedKeyTest {
                 }
 
                 @Override
-                public boolean hasPassphrase(long keyId) {
+                public boolean hasPassphrase(Long keyId) {
                     return keyId == TestKeys.CRYPTIE_KEY_ID;
                 }
             });
diff --git a/pgpainless-core/src/test/java/org/pgpainless/key/protection/SecretKeyRingProtectorTest.java b/pgpainless-core/src/test/java/org/pgpainless/key/protection/SecretKeyRingProtectorTest.java
index b6781355..a5030f74 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/key/protection/SecretKeyRingProtectorTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/key/protection/SecretKeyRingProtectorTest.java
@@ -108,12 +108,12 @@ public class SecretKeyRingProtectorTest {
         CachingSecretKeyRingProtector protector = new CachingSecretKeyRingProtector(passphraseMap,
                 KeyRingProtectionSettings.secureDefaultSettings(), new SecretKeyPassphraseProvider() {
             @Override
-            public Passphrase getPassphraseFor(long keyId) {
+            public Passphrase getPassphraseFor(Long keyId) {
                 return Passphrase.fromPassword("missingP455w0rd");
             }
 
             @Override
-            public boolean hasPassphrase(long keyId) {
+            public boolean hasPassphrase(Long keyId) {
                 return true;
             }
         });