diff --git a/src/ASiC_E.cpp b/src/ASiC_E.cpp
index 4f3f98759..5b2b584b3 100644
--- a/src/ASiC_E.cpp
+++ b/src/ASiC_E.cpp
@@ -35,8 +35,6 @@ using namespace digidoc;
 using namespace digidoc::util;
 using namespace std;
 
-constexpr string_view MANIFEST_NS {"urn:oasis:names:tc:opendocument:xmlns:manifest:1.0"};
-
 class ASiC_E::Private
 {
 public:
@@ -88,28 +86,10 @@ vector<DataFile*> ASiC_E::metaFiles() const
  *         document does not exist.
  * @throws Exception is thrown if ASiC_E class is not correctly initialized.
  */
-void ASiC_E::save(const string &path)
+void ASiC_E::save(const ZipSerialize &s)
 {
-    if(dataFiles().empty())
-        THROW("Can not save, container is empty.");
-    if(mediaType() != MIMETYPE_ASIC_E)
-        THROW("'%s' format is not supported", mediaType().c_str());
-
-    if(!path.empty())
-        zpath(path);
-    ZipSerialize s(zpath(), true);
-
-    stringstream mimetype;
-    mimetype << mediaType();
-    s.addFile("mimetype", mimetype, zproperty("mimetype"), false);
-
-    stringstream manifest;
-    if(!createManifest().save(manifest))
+    if(!createManifest().save(s.addFile("META-INF/manifest.xml", zproperty("META-INF/manifest.xml")), true))
         THROW("Failed to create manifest XML");
-    s.addFile("META-INF/manifest.xml", manifest, zproperty("META-INF/manifest.xml"));
-
-    for(const DataFile *file: dataFiles())
-        s.addFile(file->fileName(), *(static_cast<const DataFilePrivate*>(file)->m_is), zproperty(file->fileName()));
 
     std::set<Signatures*> saved;
     for(Signature *iter: signatures())
@@ -122,10 +102,8 @@ void ASiC_E::save(const string &path)
         });
         if(name == d->signatures.cend())
             THROW("Unkown signature object");
-        stringstream ofs;
-        if(!signatures->save(ofs))
+        if(!signatures->save(s.addFile(name->first, zproperty(name->first))))
             THROW("Failed to create signature XML file.");
-        s.addFile(name->first, ofs, zproperty(name->first));
     }
 }
 
@@ -159,32 +137,16 @@ void ASiC_E::addAdESSignature(istream &data)
     }
 }
 
-unique_ptr<Container> ASiC_E::openInternal(const string &path)
+void ASiC_E::canSave()
 {
-    DEBUG("ASiC_E::openInternal(%s)", path.c_str());
-    return unique_ptr<Container>(new ASiC_E(path));
+    if(mediaType() != MIMETYPE_ASIC_E)
+        THROW("'%s' format is not supported", mediaType().c_str());
 }
 
-/**
- * Creates BDoc container manifest file and returns its path.
- *
- * @return returns created manifest file path.
- * @throws Exception exception is thrown if manifest file creation failed.
- */
-XMLDocument ASiC_E::createManifest() const
+unique_ptr<Container> ASiC_E::openInternal(const string &path)
 {
-    DEBUG("ASiC_E::createManifest()");
-    auto doc = XMLDocument::create("manifest", MANIFEST_NS, "manifest");
-    doc.setProperty("version", "1.2", MANIFEST_NS);
-    auto add = [&doc](string_view path, string_view mime) {
-        auto file = doc+"file-entry";
-        file.setProperty("full-path", path, MANIFEST_NS);
-        file.setProperty("media-type", mime, MANIFEST_NS);
-    };
-    add("/", mediaType());
-    for(const DataFile *file: dataFiles())
-        add(file->fileName(), file->mediaType());
-    return doc;
+    DEBUG("ASiC_E::openInternal(%s)", path.c_str());
+    return unique_ptr<Container>(new ASiC_E(path));
 }
 
 void ASiC_E::loadSignatures(istream &data, const string &file)
diff --git a/src/ASiC_E.h b/src/ASiC_E.h
index c7887d9fb..88b0d93a1 100644
--- a/src/ASiC_E.h
+++ b/src/ASiC_E.h
@@ -23,8 +23,6 @@
 
 namespace digidoc
 {
-    struct XMLDocument;
-
     /**
      * Implements the BDOC specification of the signed digital document container.
      * Container can contain several files and all these files can be signed using
@@ -42,7 +40,6 @@ namespace digidoc
           static constexpr std::string_view ASIC_TSA_PROFILE = "time-stamp-archive";
 
           ~ASiC_E() final;
-          void save(const std::string &path = {}) final;
           std::vector<DataFile*> metaFiles() const;
 
           void addAdESSignature(std::istream &data) final;
@@ -56,9 +53,10 @@ namespace digidoc
           ASiC_E();
           ASiC_E(const std::string &path);
           DISABLE_COPY(ASiC_E);
-          XMLDocument createManifest() const;
+          void canSave() final;
           void loadSignatures(std::istream &data, const std::string &file);
           void parseManifestAndLoadFiles(const ZipSerialize &z);
+          void save(const ZipSerialize &s) final;
 
           class Private;
           std::unique_ptr<Private> d;
diff --git a/src/ASiC_S.cpp b/src/ASiC_S.cpp
index 6cd83fc4a..ac64f9be3 100644
--- a/src/ASiC_S.cpp
+++ b/src/ASiC_S.cpp
@@ -34,47 +34,51 @@ using namespace std;
 /**
  * Initialize ASiCS container.
  */
-ASiC_S::ASiC_S(): ASiContainer(MIMETYPE_ASIC_S)
+ASiC_S::ASiC_S()
+    : ASiContainer(MIMETYPE_ASIC_S)
 {}
 
 /**
  * Opens ASiC-S container from a file
  */
-ASiC_S::ASiC_S(const string &path): ASiContainer(MIMETYPE_ASIC_S)
+ASiC_S::ASiC_S(const string &path)
+    : ASiContainer(MIMETYPE_ASIC_S)
 {
     auto z = load(path, false, {mediaType()});
-    static const string_view metaInf = "META-INF/";
+    auto starts_with = [](string_view str, string_view needle) constexpr {
+        return str.size() >= needle.size() && str.compare(0, needle.size(), needle) == 0;
+    };
 
     for(const string &file: z.list())
     {
-        if(file == "mimetype" ||
-            (metaInf.size() < file.size() && file.compare(0, metaInf.size(), metaInf) == 0))
-        {
-            if(file == "META-INF/timestamp.tst")
-            {
-                if(!signatures().empty())
-                    THROW("Can not add signature to ASiC-S container which already contains a signature.");
-                addSignature(make_unique<SignatureTST>(z.extract<stringstream>(file).str(), this));
-            }
-            if(file == "META-INF/signatures.xml")
-            {
-                if(!signatures().empty())
-                    THROW("Can not add signature to ASiC-S container which already contains a signature.");
-                auto data = z.extract<stringstream>(file);
-                auto signatures = make_shared<Signatures>(data, mediaType());
-                for(auto s = signatures->signature(); s; s++)
-                    addSignature(make_unique<SignatureXAdES_LTA>(signatures, s, this));
-            }
+        if(file == "mimetype")
             continue;
+        if(file == "META-INF/timestamp.tst")
+        {
+            if(!signatures().empty())
+                THROW("Can not add signature to ASiC-S container which already contains a signature.");
+            addSignature(make_unique<SignatureTST>(z.extract<stringstream>(file).str(), this));
         }
-
-        const auto directory = File::directory(file);
-        if(directory.empty() || directory == "/" || directory == "./")
+        else if(file == "META-INF/signatures.xml")
         {
-            if(!dataFiles().empty())
-                THROW("Can not add document to ASiC-S container which already contains a document.");
-            addDataFile(dataStream(file, z), file, "application/octet-stream");
+            if(!signatures().empty())
+                THROW("Can not add signature to ASiC-S container which already contains a signature.");
+            auto data = z.extract<stringstream>(file);
+            auto signatures = make_shared<Signatures>(data, mediaType());
+            for(auto s = signatures->signature(); s; s++)
+                addSignature(make_unique<SignatureXAdES_LTA>(signatures, s, this));
         }
+        else if(file == "META-INF/ASiCArchiveManifest.xml")
+            THROW("ASiCArchiveManifest are not supported.");
+        else if(starts_with(file, "META-INF/"))
+            continue;
+        else if(const auto directory = File::directory(file);
+            !directory.empty() && directory != "/" && directory != "./")
+            THROW("Subfolders are not supported %s", directory.c_str());
+        else if(!dataFiles().empty())
+            THROW("Can not add document to ASiC-S container which already contains a document.");
+        else
+            addDataFile(dataStream(file, z), file, "application/octet-stream");
     }
 
     if(dataFiles().empty())
@@ -83,11 +87,6 @@ ASiC_S::ASiC_S(const string &path): ASiContainer(MIMETYPE_ASIC_S)
         THROW("ASiC-S container does not contain any signatures.");
 }
 
-void ASiC_S::save(const string & /*path*/)
-{
-    THROW("Not implemented.");
-}
-
 unique_ptr<Container> ASiC_S::createInternal(const string & /*path*/)
 {
     return {};
@@ -98,6 +97,12 @@ void ASiC_S::addAdESSignature(istream & /*signature*/)
     THROW("Not implemented.");
 }
 
+void ASiC_S::canSave()
+{
+    if(auto list = signatures(); !list.empty() && list.front()->profile() != ASIC_TST_PROFILE)
+        THROW("ASiC-S container supports only saving TimeStampToken signatures.");
+}
+
 unique_ptr<Container> ASiC_S::openInternal(const string &path, ContainerOpenCB * /*cb*/)
 {
     if (!isContainerSimpleFormat(path))
@@ -111,6 +116,14 @@ Signature* ASiC_S::prepareSignature(Signer * /*signer*/)
     THROW("Not implemented.");
 }
 
+void ASiC_S::save(const ZipSerialize &s)
+{
+    if(zproperty("META-INF/manifest.xml").size && !createManifest().save(s.addFile("META-INF/manifest.xml", zproperty("META-INF/manifest.xml")), true))
+        THROW("Failed to create manifest XML");
+    if(auto list = signatures(); !list.empty())
+        s.addFile("META-INF/timestamp.tst", zproperty("META-INF/timestamp.tst"))(static_cast<SignatureTST*>(list.front())->save());
+}
+
 Signature *ASiC_S::sign(Signer * /*signer*/)
 {
     THROW("Not implemented.");
diff --git a/src/ASiC_S.h b/src/ASiC_S.h
index e1a91be46..f6eba5a20 100644
--- a/src/ASiC_S.h
+++ b/src/ASiC_S.h
@@ -30,9 +30,8 @@ namespace digidoc
     */
     class ASiC_S : public ASiContainer
     {
-
     public:
-        void save(const std::string &path = {}) override;
+        static constexpr std::string_view ASIC_TST_PROFILE = "TimeStampToken";
 
         void addAdESSignature(std::istream &sigdata) override;
         Signature* prepareSignature(Signer *signer) override;
@@ -46,6 +45,9 @@ namespace digidoc
         ASiC_S(const std::string &path);
         DISABLE_COPY(ASiC_S);
 
+        void canSave() final;
+        void save(const ZipSerialize &s) final;
+
         static bool isContainerSimpleFormat(const std::string &path);
     };
 }
diff --git a/src/ASiContainer.cpp b/src/ASiContainer.cpp
index 49cc96fd4..a4c1b0ce9 100644
--- a/src/ASiContainer.cpp
+++ b/src/ASiContainer.cpp
@@ -21,10 +21,12 @@
 
 #include "DataFile_p.h"
 #include "Signature.h"
+#include "XMLDocument.h"
 #include "util/File.h"
 #include "util/log.h"
 
 #include <algorithm>
+#include <array>
 #include <ctime>
 #include <fstream>
 #include <map>
@@ -51,7 +53,23 @@ class ASiContainer::Private
 ASiContainer::ASiContainer(string_view mimetype)
     : d(make_unique<Private>())
 {
-    d->mimetype = mimetype;
+    d->mimetype = string(mimetype);
+}
+
+XMLDocument ASiContainer::createManifest() const
+{
+    DEBUG("ASiContainer::createManifest()");
+    auto doc = XMLDocument::create("manifest", MANIFEST_NS, "manifest");
+    doc.setProperty("version", "1.2", MANIFEST_NS);
+    auto add = [&doc](string_view path, string_view mime) {
+        auto file = doc+"file-entry";
+        file.setProperty("full-path", path, MANIFEST_NS);
+        file.setProperty("media-type", mime, MANIFEST_NS);
+    };
+    add("/", mediaType());
+    for(const DataFile *file: dataFiles())
+        add(file->fileName(), file->mediaType());
+    return doc;
 }
 
 /**
@@ -166,7 +184,7 @@ void ASiContainer::addDataFile(const string &path, const string &mediaType)
         is = std::move(data);
     }
     d->properties[fileName] = { appInfo(), File::modifiedTime(path), size };
-    addDataFilePrivate(std::move(is), std::move(fileName), mediaType);
+    d->documents.push_back(new DataFilePrivate(std::move(is), std::move(fileName), mediaType));
 }
 
 void ASiContainer::addDataFile(unique_ptr<istream> is, const string &fileName, const string &mediaType)
@@ -174,7 +192,7 @@ void ASiContainer::addDataFile(unique_ptr<istream> is, const string &fileName, c
     addDataFileChecks(fileName, mediaType);
     if(fileName.find_last_of("/\\") != string::npos)
         THROW("Document file '%s' cannot contain directory path.", fileName.c_str());
-    addDataFilePrivate(std::move(is), fileName, mediaType);
+    d->documents.push_back(new DataFilePrivate(std::move(is), fileName, mediaType));
 }
 
 void ASiContainer::addDataFileChecks(const string &fileName, const string &mediaType)
@@ -241,6 +259,34 @@ void ASiContainer::deleteSignature(Signature* s)
     delete s;
 }
 
+void ASiContainer::save(const string &path)
+{
+    if(dataFiles().empty())
+        THROW("Can not save, container is empty.");
+    canSave();
+    if(!path.empty())
+        zpath(path);
+    ZipSerialize s(zpath(), true);
+    s.addFile("mimetype", zproperty("mimetype"), false)(mediaType());
+
+    array<char,10240> buf{};
+    for(const DataFile *file: dataFiles())
+    {
+        auto f = s.addFile(file->fileName(), zproperty(file->fileName()));
+        const auto &is = static_cast<const DataFilePrivate*>(file)->m_is;
+        is->clear();
+        is->seekg(0);
+        while(*is)
+        {
+            is->read(buf.data(), buf.size());
+            if(auto size = is->gcount(); size > 0)
+                f(buf.data(), size_t(size));
+        }
+    }
+
+    save(s);
+}
+
 void ASiContainer::zpath(const string &file)
 {
     d->path = file;
@@ -251,11 +297,11 @@ string ASiContainer::zpath() const
     return d->path;
 }
 
-const ZipSerialize::Properties& ASiContainer::zproperty(const string &file) const
+const ZipSerialize::Properties& ASiContainer::zproperty(string_view file) const
 {
     if(auto i = d->properties.find(file); i != d->properties.cend())
         return i->second;
-    return d->properties[file] = { appInfo(), time(nullptr), 0 };
+    return d->properties[string(file)] = { appInfo(), time(nullptr), 0 };
 }
 
 /**
diff --git a/src/ASiContainer.h b/src/ASiContainer.h
index b71a076f5..cdc0b952a 100644
--- a/src/ASiContainer.h
+++ b/src/ASiContainer.h
@@ -26,6 +26,8 @@
 
 namespace digidoc
 {
+    struct XMLDocument;
+
     /**
      * Base class for the ASiC (Associated Signature Container) documents.
      * Implements the operations and data structures common for more specific ASiC
@@ -42,6 +44,7 @@ namespace digidoc
           static constexpr std::string_view MIMETYPE_ASIC_S = "application/vnd.etsi.asic-s+zip";
           //https://signa.mitsoft.lt/static/signa-web/webResources/docs/ADOC_specification_approved20090907_EN.pdf
           static constexpr std::string_view MIMETYPE_ADOC = "application/vnd.lt.archyvai.adoc-2008";
+          static constexpr std::string_view MANIFEST_NS = "urn:oasis:names:tc:opendocument:xmlns:manifest:1.0";
 
           ~ASiContainer() override;
           std::string mediaType() const override;
@@ -51,6 +54,7 @@ namespace digidoc
           std::vector<DataFile*> dataFiles() const override;
           void removeDataFile(unsigned int id) override;
           void removeSignature(unsigned int id) override;
+          void save(const std::string &path) override;
           std::vector<Signature*> signatures() const override;
 
           static std::string readMimetype(const ZipSerialize &z);
@@ -58,21 +62,23 @@ namespace digidoc
       protected:
           ASiContainer(std::string_view mimetype);
 
+          virtual void addDataFileChecks(const std::string &path, const std::string &mediaType);
           void addDataFilePrivate(std::unique_ptr<std::istream> is, std::string fileName, std::string mediaType);
           Signature* addSignature(std::unique_ptr<Signature> &&signature);
+          virtual void canSave() = 0;
+          XMLDocument createManifest() const;
           std::unique_ptr<std::iostream> dataStream(std::string_view path, const ZipSerialize &z) const;
           ZipSerialize load(const std::string &path, bool requireMimetype, const std::set<std::string_view> &supported);
+          virtual void save(const ZipSerialize &s) = 0;
           void deleteSignature(Signature* s);
 
           void zpath(const std::string &file);
           std::string zpath() const;
-          const ZipSerialize::Properties &zproperty(const std::string &file) const;
+          const ZipSerialize::Properties& zproperty(std::string_view file) const;
 
       private:
           DISABLE_COPY(ASiContainer);
 
-          void addDataFileChecks(const std::string &path, const std::string &mediaType);
-
           class Private;
           std::unique_ptr<Private> d;
     };
diff --git a/src/SiVaContainer.cpp b/src/SiVaContainer.cpp
index 81557dbd1..234c17ae9 100644
--- a/src/SiVaContainer.cpp
+++ b/src/SiVaContainer.cpp
@@ -365,7 +365,8 @@ unique_ptr<istream> SiVaContainer::parseDDoc(bool useHashCode)
             dataFile = std::string_view{};
         }
         auto result = make_unique<stringstream>();
-        doc.save(*result);
+        if(!doc.save([&result](const char *data, size_t size) { result->write(data, streamsize(size)); }))
+            THROW("Failed to save DDoc");
         return result;
     }
     catch(const Exception &)
diff --git a/src/SignatureTST.cpp b/src/SignatureTST.cpp
index 6665da184..3061efdbe 100644
--- a/src/SignatureTST.cpp
+++ b/src/SignatureTST.cpp
@@ -83,10 +83,9 @@ void SignatureTST::validate() const
     }
     try
     {
-        const string digestMethod = timestampToken->digestMethod();
-        timestampToken->verify(asicSDoc->dataFiles().front()->calcDigest(digestMethod));
-
-        if(!Exception::hasWarningIgnore(Exception::ReferenceDigestWeak) &&
+        timestampToken->verify(dataToSign());
+        if(auto digestMethod = signatureMethod();
+            !Exception::hasWarningIgnore(Exception::ReferenceDigestWeak) &&
             Digest::isWeakDigest(digestMethod))
         {
             Exception e(EXCEPTION_PARAMS("TimeStamp '%s' digest weak", digestMethod.c_str()));
@@ -105,7 +104,12 @@ void SignatureTST::validate() const
 
 std::vector<unsigned char> SignatureTST::dataToSign() const
 {
-    THROW("Not implemented.");
+    return asicSDoc->dataFiles().front()->calcDigest(signatureMethod());
+}
+
+vector<unsigned char> SignatureTST::messageImprint() const
+{
+    return timestampToken->messageImprint();
 }
 
 void SignatureTST::setSignatureValue(const std::vector<unsigned char> & /*signatureValue*/)
@@ -116,5 +120,10 @@ void SignatureTST::setSignatureValue(const std::vector<unsigned char> & /*signat
 // Xades properties
 string SignatureTST::profile() const
 {
-    return "TimeStampToken";
+    return string(ASiC_S::ASIC_TST_PROFILE);
+}
+
+std::vector<unsigned char> SignatureTST::save() const
+{
+    return *timestampToken;
 }
diff --git a/src/SignatureTST.h b/src/SignatureTST.h
index 52f159eea..b70940207 100644
--- a/src/SignatureTST.h
+++ b/src/SignatureTST.h
@@ -34,6 +34,7 @@ class SignatureTST final: public Signature
     SignatureTST(const std::string &data, ASiC_S *asicSDoc);
     ~SignatureTST();
 
+    std::vector<unsigned char> messageImprint() const override;
     std::string trustedSigningTime() const final;
 
     X509Cert TimeStampCertificate() const final;
@@ -51,9 +52,11 @@ class SignatureTST final: public Signature
     // Xades properties
     std::string profile() const final;
 
+    std::vector<unsigned char> save() const;
+
 private:
     DISABLE_COPY(SignatureTST);
-    ASiC_S *asicSDoc = nullptr;
+    ASiC_S *asicSDoc {};
     std::unique_ptr<TS> timestampToken;
 };
 
diff --git a/src/XMLDocument.h b/src/XMLDocument.h
index 63820d912..5ea27733f 100644
--- a/src/XMLDocument.h
+++ b/src/XMLDocument.h
@@ -34,7 +34,6 @@
 
 #include <memory>
 #include <istream>
-#include <ostream>
 
 namespace digidoc {
 
@@ -398,18 +397,21 @@ struct XMLDocument: public unique_xml_t<decltype(xmlFreeDoc)>, public XMLNode
             THROW("Failed to canonicalizate input");
     }
 
-    bool save(std::string_view path) const noexcept
+    bool save(std::string_view path, bool format = false) const noexcept
     {
-        return xmlSaveFormatFileEnc(path.data(), get(), "UTF-8", 0) > 0;
+        return xmlSaveFormatFileEnc(path.data(), get(), "UTF-8", format) > 0;
     }
 
-    bool save(std::ostream &os) const noexcept
+    template <typename F>
+    std::enable_if_t<std::is_invocable_v<F, const char*, size_t>, bool>
+    save(F &&f, bool format = false) const noexcept
     {
         auto *buf = xmlOutputBufferCreateIO([](void *context, const char *buffer, int len) {
-            auto *os = static_cast<std::ostream *>(context);
-            return os->write(buffer, len) ? len : -1;
-        }, nullptr, &os, nullptr);
-        return xmlSaveFormatFileTo(buf, get(), "UTF-8", 0) > 0;
+            auto *f = static_cast<F*>(context);
+            (*f)(buffer, size_t(len));
+            return len;
+        }, nullptr, &f, nullptr);
+        return xmlSaveFormatFileTo(buf, get(), "UTF-8", format) > 0;
     }
 
     void validateSchema(const std::string &schemaPath) const
diff --git a/src/XmlConf.cpp b/src/XmlConf.cpp
index 1a1ace3d6..38608d7b1 100644
--- a/src/XmlConf.cpp
+++ b/src/XmlConf.cpp
@@ -248,7 +248,7 @@ void XmlConf::Private::setUserConf(XmlConfParam<A> &param, A value)
     }
 
     File::createDirectory(File::directory(USER_CONF_LOC));
-    if(!doc.save(USER_CONF_LOC))
+    if(!doc.save(USER_CONF_LOC, true))
         ERR("Failed to save configuration: %s (%s)", USER_CONF_LOC.c_str(), SCHEMA_LOC.c_str());
 }
 
diff --git a/src/util/ZipSerialize.cpp b/src/util/ZipSerialize.cpp
index 74e5ac0f6..644633cd0 100644
--- a/src/util/ZipSerialize.cpp
+++ b/src/util/ZipSerialize.cpp
@@ -19,9 +19,10 @@
 
 #include "ZipSerialize.h"
 
+#include "Container.h"
 #include "DateTime.h"
 #include "log.h"
-#include "util/File.h"
+#include "File.h"
 
 #include <zlib.h>
 #include <minizip/unzip.h>
@@ -45,7 +46,7 @@ using namespace std;
  * @param path
  */
 ZipSerialize::ZipSerialize(const string &path, bool create)
-    : d{nullptr, create ? [](void *handle) { return zipClose(handle, nullptr); } : &unzClose}
+    : d{nullptr, create ? [](void *handle) { return zipClose(handle, appInfo().c_str()); } : &unzClose}
 {
     zlib_filefunc_def def {};
 #ifdef _WIN32
@@ -166,9 +167,10 @@ template stringstream ZipSerialize::extract<stringstream>(string_view file) cons
  * @param containerPath file path inside ZIP file.
  * @param prop Properties added for file in ZIP file.
  * @param compress File should be compressed in ZIP file.
- * @throws IOException throws exception if there were errors during locating files in zip.
+ * @return Write struct for data input
+ * @throws Exception throws exception if there were errors during locating files in zip.
  */
-void ZipSerialize::addFile(const string& containerPath, istream &is, const Properties &prop, bool compress)
+ZipSerialize::Write ZipSerialize::addFile(string_view containerPath, const Properties &prop, bool compress) const
 {
     if(!d)
         THROW("Zip file is not open");
@@ -190,26 +192,7 @@ void ZipSerialize::addFile(const string& containerPath, istream &is, const Prope
     if(zipResult != ZIP_OK)
         THROW("Failed to create new file inside ZIP container. ZLib error: %d", zipResult);
 
-    is.clear();
-    is.seekg(0);
-    array<char,10240> buf{};
-    while(is)
-    {
-        is.read(buf.data(), buf.size());
-        if(is.gcount() <= 0)
-            break;
-
-        zipResult = zipWriteInFileInZip(d.get(), buf.data(), unsigned(is.gcount()));
-        if(zipResult != ZIP_OK)
-        {
-            zipCloseFileInZip(d.get());
-            THROW("Failed to write bytes to current file inside ZIP container. ZLib error: %d", zipResult);
-        }
-    }
-
-    zipResult = zipCloseFileInZip(d.get());
-    if(zipResult != ZIP_OK)
-        THROW("Failed to close current file inside ZIP container. ZLib error: %d", zipResult);
+    return {{d.get(), zipCloseFileInZip}};
 }
 
 ZipSerialize::Properties ZipSerialize::properties(const string &file) const
@@ -239,3 +222,9 @@ ZipSerialize::Properties ZipSerialize::properties(const string &file) const
 
     return prop;
 }
+
+void ZipSerialize::Write::operator()(const void *data, size_t size) const
+{
+    if(auto result = zipWriteInFileInZip(d.get(), data, unsigned(size)); result != ZIP_OK)
+        THROW("Failed to write bytes to current file inside ZIP container. ZLib error: %d", result);
+}
diff --git a/src/util/ZipSerialize.h b/src/util/ZipSerialize.h
index 6e8c82075..4f140e5fe 100644
--- a/src/util/ZipSerialize.h
+++ b/src/util/ZipSerialize.h
@@ -33,6 +33,16 @@ namespace digidoc
     class ZipSerialize
     {
       public:
+          struct Write {
+              void operator ()(const void *data, size_t size) const;
+              template<class T>
+              constexpr void operator ()(const T &data) const
+              {
+                  operator ()(data.data(), data.size());
+              }
+              std::unique_ptr<void, int (*)(void*)> d;
+          };
+
           struct Properties {
               std::string comment;
               time_t time;
@@ -44,7 +54,7 @@ namespace digidoc
           std::vector<std::string> list() const;
           template<class T>
           T extract(std::string_view file) const;
-          void addFile(const std::string &containerPath, std::istream &is, const Properties &prop, bool compress = true);
+          Write addFile(std::string_view containerPath, const Properties &prop, bool compress = true) const;
           Properties properties(const std::string &file) const;
 
       private: