diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/protection/UnlockSecretKey.java b/pgpainless-core/src/main/java/org/pgpainless/key/protection/UnlockSecretKey.java
deleted file mode 100644
index 154a1aa1..00000000
--- a/pgpainless-core/src/main/java/org/pgpainless/key/protection/UnlockSecretKey.java
+++ /dev/null
@@ -1,67 +0,0 @@
-// Copyright 2021 Paul Schaub.
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package org.pgpainless.key.protection;
-
-import org.bouncycastle.openpgp.PGPException;
-import org.bouncycastle.openpgp.PGPPrivateKey;
-import org.bouncycastle.openpgp.PGPSecretKey;
-import org.bouncycastle.openpgp.operator.PBESecretKeyDecryptor;
-import org.pgpainless.PGPainless;
-import org.pgpainless.exception.KeyIntegrityException;
-import org.pgpainless.exception.WrongPassphraseException;
-import org.pgpainless.key.info.KeyInfo;
-import org.pgpainless.key.util.PublicKeyParameterValidationUtil;
-import org.pgpainless.util.Passphrase;
-
-public final class UnlockSecretKey {
-
-    private UnlockSecretKey() {
-
-    }
-
-    public static PGPPrivateKey unlockSecretKey(PGPSecretKey secretKey, SecretKeyRingProtector protector)
-            throws PGPException, KeyIntegrityException {
-
-        PBESecretKeyDecryptor decryptor = null;
-        if (KeyInfo.isEncrypted(secretKey)) {
-            decryptor = protector.getDecryptor(secretKey.getKeyID());
-        }
-        PGPPrivateKey privateKey = unlockSecretKey(secretKey, decryptor);
-        return privateKey;
-    }
-
-    public static PGPPrivateKey unlockSecretKey(PGPSecretKey secretKey, PBESecretKeyDecryptor decryptor)
-            throws PGPException {
-        PGPPrivateKey privateKey;
-        try {
-            privateKey = secretKey.extractPrivateKey(decryptor);
-        } catch (PGPException e) {
-            throw new WrongPassphraseException(secretKey.getKeyID(), e);
-        }
-
-        if (privateKey == null) {
-            int s2kType = secretKey.getS2K().getType();
-            if (s2kType >= 100 && s2kType <= 110) {
-                throw new PGPException("Cannot decrypt secret key" + Long.toHexString(secretKey.getKeyID()) + ": " +
-                        "Unsupported private S2K usage type " + s2kType);
-            }
-
-            throw new PGPException("Cannot decrypt secret key.");
-        }
-
-        if (PGPainless.getPolicy().isEnableKeyParameterValidation()) {
-            PublicKeyParameterValidationUtil.verifyPublicKeyParameterIntegrity(privateKey, secretKey.getPublicKey());
-        }
-
-        return privateKey;
-    }
-
-    public static PGPPrivateKey unlockSecretKey(PGPSecretKey secretKey, Passphrase passphrase)
-            throws PGPException, KeyIntegrityException {
-        return unlockSecretKey(secretKey, SecretKeyRingProtector.unlockSingleKeyWith(
-                passphrase == null ? Passphrase.emptyPassphrase() : passphrase, secretKey));
-    }
-}
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/OpenPgpMessageInputStream.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/OpenPgpMessageInputStream.kt
index a255e90e..1f34ec23 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/OpenPgpMessageInputStream.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/OpenPgpMessageInputStream.kt
@@ -350,7 +350,7 @@ class OpenPgpMessageInputStream(
                 }
 
                 LOGGER.debug("Attempt decryption with key $decryptionKeyId while interactively requesting its passphrase.")
-                val protector = options.getSecretKeyProtector(decryptionKeys)
+                val protector = options.getSecretKeyProtector(decryptionKeys) ?: continue
                 val privateKey = UnlockSecretKey.unlockSecretKey(secretKey, protector)
                 if (decryptWithPrivateKey(esks, privateKey, decryptionKeyId, pkesk)) {
                     return true
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/UnlockSecretKey.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/UnlockSecretKey.kt
new file mode 100644
index 00000000..533b33a7
--- /dev/null
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/UnlockSecretKey.kt
@@ -0,0 +1,68 @@
+// Copyright 2023 Paul Schaub.
+// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.key.protection
+
+import org.bouncycastle.openpgp.PGPException
+import org.bouncycastle.openpgp.PGPPrivateKey
+import org.bouncycastle.openpgp.PGPSecretKey
+import org.bouncycastle.openpgp.operator.PBESecretKeyDecryptor
+import org.pgpainless.PGPainless
+import org.pgpainless.exception.KeyIntegrityException
+import org.pgpainless.exception.WrongPassphraseException
+import org.pgpainless.key.info.KeyInfo
+import org.pgpainless.key.util.KeyIdUtil
+import org.pgpainless.key.util.PublicKeyParameterValidationUtil
+import org.pgpainless.util.Passphrase
+import kotlin.jvm.Throws
+
+class UnlockSecretKey {
+
+    companion object {
+
+        @JvmStatic
+        @Throws(PGPException::class, KeyIntegrityException::class)
+        fun unlockSecretKey(secretKey: PGPSecretKey, protector: SecretKeyRingProtector): PGPPrivateKey {
+            return if (KeyInfo.isEncrypted(secretKey)) {
+                unlockSecretKey(secretKey, protector.getDecryptor(secretKey.keyID))
+            } else {
+                unlockSecretKey(secretKey, null as PBESecretKeyDecryptor?)
+            }
+        }
+
+        @JvmStatic
+        @Throws(PGPException::class)
+        fun unlockSecretKey(secretKey: PGPSecretKey, decryptor: PBESecretKeyDecryptor?): PGPPrivateKey {
+            val privateKey = try {
+                secretKey.extractPrivateKey(decryptor)
+            } catch (e : PGPException) {
+                throw WrongPassphraseException(secretKey.keyID, e)
+            }
+
+            if (privateKey == null) {
+                if (secretKey.s2K.type in 100..110) {
+                    throw PGPException("Cannot decrypt secret key ${KeyIdUtil.formatKeyId(secretKey.keyID)}: \n" +
+                            "Unsupported private S2K type ${secretKey.s2K.type}")
+                }
+                throw PGPException("Cannot decrypt secret key.")
+            }
+
+            if (PGPainless.getPolicy().isEnableKeyParameterValidation()) {
+                PublicKeyParameterValidationUtil.verifyPublicKeyParameterIntegrity(privateKey, secretKey.publicKey)
+            }
+
+            return privateKey
+        }
+
+        @JvmStatic
+        fun unlockSecretKey(secretKey: PGPSecretKey, passphrase: Passphrase?): PGPPrivateKey {
+            return if (passphrase == null) {
+                unlockSecretKey(secretKey, SecretKeyRingProtector.unprotectedKeys())
+            } else {
+                unlockSecretKey(secretKey, SecretKeyRingProtector.unlockSingleKeyWith(passphrase, secretKey))
+            }
+        }
+    }
+}
\ No newline at end of file