diff --git a/pgpainless-core/src/main/kotlin/org/bouncycastle/extensions/PGPKeyRingExtensions.kt b/pgpainless-core/src/main/kotlin/org/bouncycastle/extensions/PGPKeyRingExtensions.kt
new file mode 100644
index 00000000..43669bd1
--- /dev/null
+++ b/pgpainless-core/src/main/kotlin/org/bouncycastle/extensions/PGPKeyRingExtensions.kt
@@ -0,0 +1,15 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.bouncycastle.extensions
+
+import org.bouncycastle.openpgp.PGPKeyRing
+import org.pgpainless.key.SubkeyIdentifier
+
+/**
+ * Return true, if this [PGPKeyRing] contains the subkey identified by the [SubkeyIdentifier].
+ */
+fun PGPKeyRing.matches(subkeyIdentifier: SubkeyIdentifier): Boolean =
+        this.publicKey.keyID == subkeyIdentifier.primaryKeyId &&
+                this.getPublicKey(subkeyIdentifier.subkeyId) != null
\ No newline at end of file
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt
index 8719cef7..3eb49e5d 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt
@@ -4,6 +4,7 @@
 
 package org.pgpainless.decryption_verification
 
+import org.bouncycastle.extensions.matches
 import org.bouncycastle.openpgp.PGPKeyRing
 import org.bouncycastle.openpgp.PGPLiteralData
 import org.pgpainless.algorithm.CompressionAlgorithm
@@ -227,10 +228,9 @@ class MessageMetadata(
      */
     @JvmOverloads
     fun isAuthenticatablySignedBy(userId: String, email: Boolean, certificateAuthority: CertificateAuthority, targetAmount: Int = 120): Boolean {
-        return verifiedSignatures.any {
-            certificateAuthority.authenticateBinding(
-                    it.signingKey.fingerprint, userId, email, it.signature.creationTime, targetAmount
-            ).authenticated
+        return verifiedSignatures.any { certificateAuthority
+                .authenticateBinding(it.signingKey.fingerprint, userId, email, it.signature.creationTime, targetAmount)
+                .authenticated
         }
     }
 
@@ -241,31 +241,23 @@ class MessageMetadata(
      * @param fingerprint fingerprint
      * @return true if message was signed by a cert identified by the given fingerprint
      */
-    fun isVerifiedSignedBy(fingerprint: OpenPgpFingerprint) = verifiedSignatures.any {
-        it.signingKey.primaryKeyFingerprint == fingerprint || it.signingKey.subkeyFingerprint == fingerprint
-    }
+    fun isVerifiedSignedBy(fingerprint: OpenPgpFingerprint) =
+            verifiedSignatures.any { it.signingKey.matches(fingerprint) }
 
-    fun isVerifiedSignedBy(keys: PGPKeyRing) = containsSignatureBy(verifiedSignatures, keys)
+    fun isVerifiedSignedBy(keys: PGPKeyRing) =
+            verifiedSignatures.any { keys.matches(it.signingKey) }
 
-    fun isVerifiedDetachedSignedBy(fingerprint: OpenPgpFingerprint) = verifiedDetachedSignatures.any {
-        it.signingKey.primaryKeyFingerprint == fingerprint || it.signingKey.subkeyFingerprint == fingerprint
-    }
+    fun isVerifiedDetachedSignedBy(fingerprint: OpenPgpFingerprint) =
+            verifiedDetachedSignatures.any { it.signingKey.matches(fingerprint) }
 
-    fun isVerifiedDetachedSignedBy(keys: PGPKeyRing) = containsSignatureBy(verifiedDetachedSignatures, keys)
+    fun isVerifiedDetachedSignedBy(keys: PGPKeyRing) =
+            verifiedDetachedSignatures.any { keys.matches(it.signingKey) }
 
-    fun isVerifiedInlineSignedBy(fingerprint: OpenPgpFingerprint) = verifiedInlineSignatures.any {
-        it.signingKey.primaryKeyFingerprint == fingerprint || it.signingKey.subkeyFingerprint == fingerprint
-    }
+    fun isVerifiedInlineSignedBy(fingerprint: OpenPgpFingerprint) =
+            verifiedInlineSignatures.any { it.signingKey.matches(fingerprint) }
 
-    fun isVerifiedInlineSignedBy(keys: PGPKeyRing) = containsSignatureBy(verifiedInlineSignatures, keys)
-
-    private fun containsSignatureBy(signatures: List<SignatureVerification>, keys: PGPKeyRing) =
-            signatures.any {
-                // Match certificate by primary key id
-                keys.publicKey.keyID == it.signingKey.primaryKeyId &&
-                        // match signing subkey
-                        keys.getPublicKey(it.signingKey.subkeyId) != null
-            }
+    fun isVerifiedInlineSignedBy(keys: PGPKeyRing) =
+            verifiedInlineSignatures.any { keys.matches(it.signingKey) }
 
     // ################################################################################################################
     // ###                                             Literal Data                                                 ###
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/encryption_signing/EncryptionResult.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/encryption_signing/EncryptionResult.kt
index fd9febc7..0e9a40c9 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/encryption_signing/EncryptionResult.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/encryption_signing/EncryptionResult.kt
@@ -4,6 +4,7 @@
 
 package org.pgpainless.encryption_signing
 
+import org.bouncycastle.extensions.matches
 import org.bouncycastle.openpgp.PGPLiteralData
 import org.bouncycastle.openpgp.PGPPublicKeyRing
 import org.bouncycastle.openpgp.PGPSignature
@@ -39,10 +40,7 @@ data class EncryptionResult(
      * @param certificate certificate
      * @return true if encrypted for 1+ subkeys, false otherwise.
      */
-    fun isEncryptedFor(certificate: PGPPublicKeyRing) = recipients.any {
-        certificate.publicKey.keyID == it.primaryKeyId &&
-                certificate.getPublicKey(it.subkeyId) != null
-    }
+    fun isEncryptedFor(certificate: PGPPublicKeyRing) = recipients.any { certificate.matches(it) }
 
     companion object {
         /**
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/SubkeyIdentifier.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/SubkeyIdentifier.kt
index ea36913c..58e7719c 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/key/SubkeyIdentifier.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/SubkeyIdentifier.kt
@@ -31,6 +31,9 @@ class SubkeyIdentifier(
     val subkeyId = subkeyFingerprint.keyId
     val primaryKeyId = primaryKeyFingerprint.keyId
 
+    fun matches(fingerprint: OpenPgpFingerprint) =
+            primaryKeyFingerprint == fingerprint || subkeyFingerprint == fingerprint
+
     override fun equals(other: Any?): Boolean {
         if (other == null) {
             return false