diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 72e56eb19..1c5e199bc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,352 +1,353 @@
 # SPDX-License-Identifier: CC0-1.0
 # SPDX-FileCopyrightText: none
 # target_include_directories does not handle empty include paths
 include_directories(
     ${Boost_INCLUDE_DIRS}
     ${GPGME_INCLUDES}
 )
 
 add_definitions(-DTRANSLATION_DOMAIN=\"libkleopatra\")
 
 #add_definitions( -DQT_NO_CAST_FROM_ASCII )
 #add_definitions( -DQT_NO_CAST_TO_ASCII )
 
 kde_enable_exceptions()
 
 add_definitions( -DGPGMEPP_ERR_SOURCE_DEFAULT=13 ) # 13 is GPG_ERR_SOURCE_KLEO, even if gpg-error's too old to know about
 
 add_subdirectory( pics )
 if (BUILD_TESTING)
    add_subdirectory( tests )
 endif()
 add_library(KF5Libkleo)
 add_library(KF5::Libkleo ALIAS KF5Libkleo)
 
 ########### next target ###############
 target_sources(KF5Libkleo PRIVATE
    kleo/checksumdefinition.cpp
    kleo/checksumdefinition.h
    kleo/debug.cpp
    kleo/debug.h
    kleo/defaultkeyfilter.cpp
    kleo/defaultkeyfilter.h
    kleo/defaultkeygenerationjob.cpp
    kleo/defaultkeygenerationjob.h
    kleo/docaction.cpp
    kleo/dn.cpp
    kleo/dn.h
    kleo/enum.cpp
    kleo/enum.h
    kleo/kconfigbasedkeyfilter.cpp
    kleo/kconfigbasedkeyfilter.h
    kleo/keyfilter.h
    kleo/keyfiltermanager.cpp
    kleo/keyfiltermanager.h
    kleo/keygroup.cpp
    kleo/keygroup.h
    kleo/keygroupconfig.cpp
    kleo/keygroupconfig.h
    kleo/keygroupimportexport.cpp
    kleo/keygroupimportexport.h
    kleo/keyresolver.cpp
    kleo/keyresolver.h
    kleo/keyresolvercore.cpp
    kleo/keyresolvercore.h
    kleo/keyserverconfig.cpp
    kleo/keyserverconfig.h
    kleo/kleoexception.cpp
    kleo/kleoexception.h
    kleo/oidmap.cpp
    kleo/oidmap.h
    kleo/predicates.h
    kleo/stl_util.h
    models/keycache.cpp
    models/keycache.h
    models/keycache_p.h
    models/keylist.h
    models/keylistmodel.cpp
    models/keylistmodel.h
    models/keylistmodelinterface.cpp
    models/keylistmodelinterface.h
    models/keylistsortfilterproxymodel.cpp
    models/keylistsortfilterproxymodel.h
    models/keyrearrangecolumnsproxymodel.cpp
    models/keyrearrangecolumnsproxymodel.h
    models/subkeylistmodel.cpp
    models/subkeylistmodel.h
    models/useridlistmodel.cpp
    models/useridlistmodel.h
    utils/algorithm.h
    utils/assuan.cpp
    utils/assuan.h
    utils/classify.cpp
    utils/classify.h
    utils/compat.cpp
    utils/compat.h
    utils/cryptoconfig.cpp
    utils/cryptoconfig.h
    utils/cryptoconfig_p.h
    utils/filesystemwatcher.cpp
    utils/filesystemwatcher.h
    utils/formatting.cpp
    utils/formatting.h
    utils/gnupg-registry.c
    utils/gnupg-registry.h
    utils/gnupg.cpp
    utils/gnupg.h
    utils/hex.cpp
    utils/hex.h
+   utils/keyhelpers.cpp
    utils/keyhelpers.h
    utils/qtstlhelpers.cpp
    utils/qtstlhelpers.h
    utils/scdaemon.cpp
    utils/scdaemon.h
    utils/stringutils.cpp
    utils/stringutils.h
    utils/test.cpp
    utils/test.h
    utils/uniquelock.cpp
    utils/uniquelock.h
    )
 ecm_qt_declare_logging_category(KF5Libkleo HEADER libkleo_debug.h IDENTIFIER LIBKLEO_LOG CATEGORY_NAME org.kde.pim.libkleo
         DESCRIPTION "libkleo (kleo_core)"
         EXPORT LIBKLEO
     )
 
 
 target_sources(KF5Libkleo PRIVATE
    ui/auditlogviewer.cpp
    ui/auditlogviewer.h
    ui/cryptoconfigentryreaderport.cpp
    ui/cryptoconfigentryreaderport_p.h
    ui/cryptoconfigmodule.cpp
    ui/cryptoconfigmodule.h
    ui/cryptoconfigmodule_p.h
    ui/directoryserviceswidget.cpp
    ui/directoryserviceswidget.h
    ui/dnattributeorderconfigwidget.cpp
    ui/dnattributeorderconfigwidget.h
    ui/editdirectoryservicedialog.cpp
    ui/editdirectoryservicedialog.h
    ui/filenamerequester.cpp
    ui/filenamerequester.h
    ui/kdhorizontalline.cpp
    ui/kdhorizontalline.h
    ui/messagebox.cpp
    ui/messagebox.h
    ui/progressbar.cpp
    ui/progressbar.h
    ui/progressdialog.cpp
    ui/progressdialog.h
    )
 
 ecm_qt_declare_logging_category(KF5Libkleo HEADER kleo_ui_debug.h IDENTIFIER KLEO_UI_LOG CATEGORY_NAME org.kde.pim.kleo_ui
         DESCRIPTION "libkleo (kleo_ui)"
         OLD_CATEGORY_NAMES log_kleo_ui
         EXPORT LIBKLEO
     )
 
 
 target_sources(KF5Libkleo PRIVATE    # make this a separate lib.
     ui/keyapprovaldialog.cpp
     ui/keyapprovaldialog.h
     ui/keylistview.cpp
     ui/keylistview.h
     ui/keyrequester.cpp
     ui/keyrequester.h
     ui/keyselectioncombo.cpp
     ui/keyselectioncombo.h
     ui/keyselectiondialog.cpp
     ui/keyselectiondialog.h
     ui/newkeyapprovaldialog.cpp
     ui/newkeyapprovaldialog.h
     )
 
 
 target_link_libraries(KF5Libkleo PUBLIC QGpgme Gpgmepp PRIVATE Qt${QT_MAJOR_VERSION}::Widgets
                                                 KF5::I18n
                                                 KF5::Completion
                                                 KF5::ConfigCore
                                                 KF5::CoreAddons
                                                 KF5::WidgetsAddons
                                                 KF5::ItemModels
                                                 KF5::Codecs)
 
 # Boost::headers may not be available for old versions of Boost
 if (TARGET Boost::headers)
   target_link_libraries(KF5Libkleo PRIVATE Boost::headers)
 endif()
 
 if (KF5PimTextEdit_FOUND)
   add_definitions(-DHAVE_PIMTEXTEDIT)
   target_link_libraries(KF5Libkleo PRIVATE KF5::PimTextEdit)
 endif()
 
 if (COMPILE_WITH_UNITY_CMAKE_SUPPORT)
     set_target_properties(KF5Libkleo PROPERTIES UNITY_BUILD ON)
 endif()
 generate_export_header(KF5Libkleo BASE_NAME kleo)
 if(WIN32)
     target_link_libraries(KF5Libkleo ${GPGME_VANILLA_LIBRARIES} )
 endif()
 
 set_target_properties(KF5Libkleo PROPERTIES
     VERSION ${LIBKLEO_VERSION}
     SOVERSION ${LIBKLEO_SOVERSION}
     EXPORT_NAME Libkleo
 )
 
 install(TARGETS
     KF5Libkleo
     EXPORT KF5LibkleoTargets ${KF5_INSTALL_TARGETS_DEFAULT_ARGS}
 )
 
 target_include_directories(KF5Libkleo INTERFACE "$<INSTALL_INTERFACE:${KDE_INSTALL_INCLUDEDIR_KF}/Libkleo/>")
 target_include_directories(KF5Libkleo PUBLIC "$<BUILD_INTERFACE:${libkleo_SOURCE_DIR}/src;${libkleo_BINARY_DIR}/src>")
 
 ecm_generate_headers(libkleo_CamelCase_HEADERS
   HEADER_NAMES
   ChecksumDefinition
   Debug
   DefaultKeyFilter
   DefaultKeyGenerationJob
   DocAction
   Dn
   Enum
   KConfigBasedKeyFilter
   KeyFilter
   KeyFilterManager
   KeyGroup
   KeyGroupConfig
   KeyGroupImportExport
   KeyResolver
   KeyResolverCore
   KeyserverConfig
   KleoException
   OidMap
   Predicates
   Stl_Util
   REQUIRED_HEADERS libkleo_HEADERS
   PREFIX Libkleo
   RELATIVE kleo
 )
 
 ecm_generate_headers(libkleo_CamelCase_models_HEADERS
   HEADER_NAMES
   KeyCache
   KeyList
   KeyListModel
   KeyListModelInterface
   KeyListSortFilterProxyModel
   KeyRearrangeColumnsProxyModel
   SubkeyListModel
   UserIDListModel
   REQUIRED_HEADERS libkleo_models_HEADERS
   PREFIX Libkleo
   RELATIVE models
 )
 
 ecm_generate_headers(libkleo_CamelCase_utils_HEADERS
   HEADER_NAMES
   Algorithm
   Assuan
   Classify
   Compat
   CryptoConfig
   FileSystemWatcher
   Formatting
   GnuPG
   Hex
   KeyHelpers
   QtStlHelpers
   SCDaemon
   StringUtils
   Test
   UniqueLock
   REQUIRED_HEADERS libkleo_utils_HEADERS
   PREFIX Libkleo
   RELATIVE utils
 )
 
 ecm_generate_headers(libkleo_CamelCase_ui_HEADERS
   HEADER_NAMES
   CryptoConfigModule
   DNAttributeOrderConfigWidget
   DirectoryServicesWidget
   EditDirectoryServiceDialog
   FileNameRequester
   KDHorizontalLine
   KeyApprovalDialog
   KeyRequester
   KeySelectionCombo
   KeySelectionDialog
   MessageBox
   NewKeyApprovalDialog
   ProgressDialog
   REQUIRED_HEADERS libkleo_ui_HEADERS
   PREFIX Libkleo
   RELATIVE ui
 )
 
 ecm_generate_pri_file(BASE_NAME Libkleo
     LIB_NAME KF5Libkleo
     DEPS "QGpgme" FILENAME_VAR PRI_FILENAME INCLUDE_INSTALL_DIR ${KDE_INSTALL_INCLUDEDIR_KF}/Libkleo
 )
 
 
 install(FILES
     ${libkleo_CamelCase_HEADERS}
     ${libkleo_CamelCase_models_HEADERS}
     ${libkleo_CamelCase_ui_HEADERS}
     ${libkleo_CamelCase_utils_HEADERS}
     DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/Libkleo/Libkleo
     COMPONENT Devel
 )
 
 install(FILES
     ${CMAKE_CURRENT_BINARY_DIR}/kleo_export.h
     ${libkleo_HEADERS}
     ${libkleo_models_HEADERS}
     ${libkleo_ui_HEADERS}
     ${libkleo_utils_HEADERS}
     DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/Libkleo/libkleo
     COMPONENT Devel
 )
 install(FILES
     ${PRI_FILENAME}
     DESTINATION ${ECM_MKSPECS_INSTALL_DIR})
 
 
 if ( WIN32 )
     install ( FILES libkleopatrarc-win32.desktop DESTINATION ${KDE_INSTALL_CONFDIR} RENAME libkleopatrarc )
 else ()
     install ( FILES libkleopatrarc.desktop DESTINATION ${KDE_INSTALL_CONFDIR} RENAME libkleopatrarc )
 endif ()
 
 if (BUILD_QCH)
     ecm_add_qch(
         KF5Libkleo_QCH
         NAME KF5Libkleo
         BASE_NAME KF5Libkleo
         VERSION ${PIM_VERSION}
         ORG_DOMAIN org.kde
         SOURCES # using only public headers, to cover only public API
         ${libkleo_HEADERS}
         ${libkleo_models_HEADERS}
         ${libkleo_ui_HEADERS}
         ${libkleo_utils_HEADERS}
         #MD_MAINPAGE "${CMAKE_SOURCE_DIR}/README.md"
         #IMAGE_DIRS "${CMAKE_SOURCE_DIR}/docs/pics"
         LINK_QCHS
             Qt5Core_QCH
             Qt5Gui_QCH
             Qt5Widgets_QCH
         INCLUDE_DIRS
             ${CMAKE_CURRENT_BINARY_DIR}
         BLANK_MACROS
             KLEO_EXPORT
         TAGFILE_INSTALL_DESTINATION ${KDE_INSTALL_QTQCHDIR}
         QCH_INSTALL_DESTINATION ${KDE_INSTALL_QTQCHDIR}
         COMPONENT Devel
     )
 endif()
diff --git a/src/utils/keyhelpers.cpp b/src/utils/keyhelpers.cpp
new file mode 100644
index 000000000..5efee9758
--- /dev/null
+++ b/src/utils/keyhelpers.cpp
@@ -0,0 +1,74 @@
+/*
+    utils/keyhelpers.cpp
+
+    This file is part of libkleopatra, the KDE keymanagement library
+    SPDX-FileCopyrightText: 2022 g10 Code GmbH
+    SPDX-FileContributor: Ingo Klöcker <dev@ingo-kloecker.de>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#include "keyhelpers.h"
+
+#include "models/keycache.h"
+
+#include <gpgme++/key.h>
+
+using namespace Kleo;
+
+namespace
+{
+bool havePublicKeyForSignature(const GpgME::UserID::Signature &signature)
+{
+    // GnuPG returns status "NoPublicKey" for missing signing keys, but also
+    // for expired or revoked signing keys.
+    return (signature.status() != GpgME::UserID::Signature::NoPublicKey)
+        || !KeyCache::instance()->findByKeyIDOrFingerprint(signature.signerKeyID()).isNull();
+}
+
+auto _getMissingSignerKeyIds(const std::vector<GpgME::UserID::Signature> &signatures)
+{
+    return std::accumulate(
+        std::begin(signatures), std::end(signatures),
+        std::set<QString>{},
+        [](auto &keyIds, const auto &signature) {
+            if (!havePublicKeyForSignature(signature)) {
+                keyIds.insert(QLatin1String{signature.signerKeyID()});
+            }
+            return keyIds;
+        }
+    );
+}
+}
+
+std::set<QString> Kleo::getMissingSignerKeyIds(const std::vector<GpgME::UserID> &userIds)
+{
+    return std::accumulate(
+        std::begin(userIds), std::end(userIds),
+        std::set<QString>{},
+        [](auto &keyIds, const auto &userID) {
+            if (!userID.isBad()) {
+                const auto newKeyIds = _getMissingSignerKeyIds(userID.signatures());
+                std::copy(std::begin(newKeyIds), std::end(newKeyIds),
+                          std::inserter(keyIds, std::end(keyIds)));
+            }
+            return keyIds;
+        }
+    );
+}
+
+std::set<QString> Kleo::getMissingSignerKeyIds(const std::vector<GpgME::Key> &keys)
+{
+    return std::accumulate(
+        std::begin(keys), std::end(keys),
+        std::set<QString>{},
+        [](auto &keyIds, const auto &key) {
+            if (!key.isBad()) {
+                const auto newKeyIds = getMissingSignerKeyIds(key.userIDs());
+                std::copy(std::begin(newKeyIds), std::end(newKeyIds),
+                          std::inserter(keyIds, std::end(keyIds)));
+            }
+            return keyIds;
+        }
+    );
+}
diff --git a/src/utils/keyhelpers.h b/src/utils/keyhelpers.h
index 69f4b5f64..1622c42d0 100644
--- a/src/utils/keyhelpers.h
+++ b/src/utils/keyhelpers.h
@@ -1,35 +1,49 @@
 /*
     utils/keyhelpers.h
 
     This file is part of libkleopatra, the KDE keymanagement library
-    SPDX-FileCopyrightText: 2021 g10 Code GmbH
+    SPDX-FileCopyrightText: 2021-2022 g10 Code GmbH
     SPDX-FileContributor: Ingo Klöcker <dev@ingo-kloecker.de>
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 
 #pragma once
 
 #include <QStringList>
 
 #include <algorithm>
+#include <set>
+#include <vector>
+
+#include "kleo_export.h"
+
+namespace GpgME
+{
+class Key;
+class UserID;
+}
 
 namespace Kleo
 {
 
 template<typename KeyContainer>
 QStringList getFingerprints(const KeyContainer &keys)
 {
     QStringList fingerprints;
 
     fingerprints.reserve(keys.size());
     std::transform(std::begin(keys), std::end(keys),
                    std::back_inserter(fingerprints),
                    [](const auto &key) {
                        return QString::fromLatin1(key.primaryFingerprint());
                    });
 
     return fingerprints;
 }
 
+KLEO_EXPORT std::set<QString> getMissingSignerKeyIds(const std::vector<GpgME::UserID> &userIds);
+
+KLEO_EXPORT std::set<QString> getMissingSignerKeyIds(const std::vector<GpgME::Key> &keys);
+
 }