--- a/CMakeLists.txt	Fri Nov 09 10:42:00 2012 +0100
+++ b/CMakeLists.txt	Fri Nov 09 11:13:29 2012 +0100
@@ -102,6 +102,7 @@
   Core/DicomFormat/DicomMap.cpp
   Core/DicomFormat/DicomTag.cpp
   Core/DicomFormat/DicomIntegerPixelAccessor.cpp
+  Core/DicomFormat/DicomInstanceHasher.cpp
   Core/FileStorage.cpp
   Core/HttpServer/EmbeddedResourceHttpHandler.cpp
   Core/HttpServer/FilesystemHttpHandler.cpp

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Core/DicomFormat/DicomInstanceHasher.cpp	Fri Nov 09 11:13:29 2012 +0100
@@ -0,0 +1,82 @@
+/**
+ * Orthanc - A Lightweight, RESTful DICOM Store
+ * Copyright (C) 2012 Medical Physics Department, CHU of Liege,
+ * Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * In addition, as a special exception, the copyright holders of this
+ * program give permission to link the code of its release with the
+ * OpenSSL project's "OpenSSL" library (or with modified versions of it
+ * that use the same license as the "OpenSSL" library), and distribute
+ * the linked executables. You must obey the GNU General Public License
+ * in all respects for all of the code used other than "OpenSSL". If you
+ * modify file(s) with this exception, you may extend this exception to
+ * your version of the file(s), but you are not obligated to do so. If
+ * you do not wish to do so, delete this exception statement from your
+ * version. If you delete this exception statement from all source files
+ * in the program, then also delete it here.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+#include "DicomInstanceHasher.h"
+
+#include "../OrthancException.h"
+#include "../Toolbox.h"
+
+namespace Orthanc
+{
+  DicomInstanceHasher::DicomInstanceHasher(const DicomMap& instance)
+  {
+    patientId_ = instance.GetValue(DICOM_TAG_PATIENT_ID).AsString();
+    instanceUid_ = instance.GetValue(DICOM_TAG_SOP_INSTANCE_UID).AsString();
+    seriesUid_ = instance.GetValue(DICOM_TAG_SERIES_INSTANCE_UID).AsString();
+    studyUid_ = instance.GetValue(DICOM_TAG_STUDY_INSTANCE_UID).AsString();
+
+    if (patientId_.size() == 0 ||
+        instanceUid_.size() == 0 ||
+        seriesUid_.size() == 0 ||
+        studyUid_.size() == 0)
+    {
+      throw OrthancException(ErrorCode_BadFileFormat);
+    }
+  }
+
+  std::string DicomInstanceHasher::HashPatient() const
+  {
+    std::string s;
+    Toolbox::ComputeSHA1(s, patientId_);
+    return s;
+  }
+
+  std::string DicomInstanceHasher::HashStudy() const
+  {
+    std::string s;
+    Toolbox::ComputeSHA1(s, patientId_ + "|" + studyUid_);
+    return s;
+  }
+
+  std::string DicomInstanceHasher::HashSeries() const
+  {
+    std::string s;
+    Toolbox::ComputeSHA1(s, patientId_ + "|" + studyUid_ + "|" + seriesUid_);
+    return s;
+  }
+
+  std::string DicomInstanceHasher::HashInstance() const
+  {
+    std::string s;
+    Toolbox::ComputeSHA1(s, patientId_ + "|" + studyUid_ + "|" + seriesUid_ + "|" + instanceUid_);
+    return s;
+  }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Core/DicomFormat/DicomInstanceHasher.h	Fri Nov 09 11:13:29 2012 +0100
@@ -0,0 +1,88 @@
+/**
+ * Orthanc - A Lightweight, RESTful DICOM Store
+ * Copyright (C) 2012 Medical Physics Department, CHU of Liege,
+ * Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * In addition, as a special exception, the copyright holders of this
+ * program give permission to link the code of its release with the
+ * OpenSSL project's "OpenSSL" library (or with modified versions of it
+ * that use the same license as the "OpenSSL" library), and distribute
+ * the linked executables. You must obey the GNU General Public License
+ * in all respects for all of the code used other than "OpenSSL". If you
+ * modify file(s) with this exception, you may extend this exception to
+ * your version of the file(s), but you are not obligated to do so. If
+ * you do not wish to do so, delete this exception statement from your
+ * version. If you delete this exception statement from all source files
+ * in the program, then also delete it here.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#pragma once
+
+#include "DicomMap.h"
+
+namespace Orthanc
+{
+  /**
+   * This class implements the hashing mechanism that is used to
+   * convert DICOM unique identifiers to Orthanc identifiers. Any
+   * Orthanc identifier for a DICOM resource corresponds to the SHA-1
+   * hash of the DICOM identifiers. 
+
+   * \note SHA-1 hash is used because it is less sensitive to
+   * collision attacks than MD5. <a
+   * href="http://en.wikipedia.org/wiki/SHA-256#Comparison_of_SHA_functions">[Reference]</a>
+   **/
+  class DicomInstanceHasher
+  {
+  private:
+    std::string patientId_;
+    std::string instanceUid_;
+    std::string seriesUid_;
+    std::string studyUid_;
+
+  public:
+    DicomInstanceHasher(const DicomMap& instance);
+
+    const std::string& GetPatientId() const
+    {
+      return patientId_;
+    }
+
+    const std::string& GetInstanceUid() const
+    {
+      return instanceUid_;
+    }
+
+    const std::string& GetSeriesUid() const
+    {
+      return seriesUid_;
+    }
+
+    const std::string& GetStudyUid() const
+    {
+      return studyUid_;
+    }
+
+    std::string HashPatient() const;
+
+    std::string HashStudy() const;
+
+    std::string HashSeries() const;
+
+    std::string HashInstance() const;
+  };
+}

--- a/OrthancServer/ServerIndex.cpp	Fri Nov 09 10:42:00 2012 +0100
+++ b/OrthancServer/ServerIndex.cpp	Fri Nov 09 11:13:29 2012 +0100
@@ -42,6 +42,7 @@
 #include "../Core/Toolbox.h"
 #include "../Core/Uuid.h"
 #include "../Core/DicomFormat/DicomArray.h"
+#include "../Core/DicomFormat/DicomInstanceHasher.h"
 #include "../Core/SQLite/Transaction.h"
 #include "FromDcmtkBridge.h"
 
@@ -530,53 +531,50 @@
   {
     boost::mutex::scoped_lock scoped_lock(mutex_);
 
-    std::string dicomPatientId = dicomSummary.GetValue(DICOM_TAG_PATIENT_ID).AsString();
-    std::string dicomInstance = dicomSummary.GetValue(DICOM_TAG_SOP_INSTANCE_UID).AsString();
-    std::string dicomSeries = dicomSummary.GetValue(DICOM_TAG_SERIES_INSTANCE_UID).AsString();
-    std::string dicomStudy = dicomSummary.GetValue(DICOM_TAG_STUDY_INSTANCE_UID).AsString();
+    DicomInstanceHasher hasher(dicomSummary);
 
     try
     {
       SQLite::Transaction t(db_);
       t.Begin();
 
-      if (HasInstance(instanceUuid, dicomInstance))
+      if (HasInstance(instanceUuid, hasher.GetInstanceUid()))
       {
         return StoreStatus_AlreadyStored;
         // TODO: Check consistency?
       }
 
       std::string patientUuid;
-      if (HasPatient(patientUuid, dicomPatientId))
+      if (HasPatient(patientUuid, hasher.GetPatientId()))
       {
         // TODO: Check consistency?
       }
       else
       {
-        patientUuid = CreatePatient(dicomPatientId, dicomSummary);
+        patientUuid = CreatePatient(hasher.GetPatientId(), dicomSummary);
       }
 
       std::string studyUuid;
-      if (HasStudy(studyUuid, dicomStudy))
+      if (HasStudy(studyUuid, hasher.GetStudyUid()))
       {
         // TODO: Check consistency?
       }
       else
       {
-        studyUuid = CreateStudy(patientUuid, dicomStudy, dicomSummary);
+        studyUuid = CreateStudy(patientUuid, hasher.GetStudyUid(), dicomSummary);
       }
 
       std::string seriesUuid;
-      if (HasSeries(seriesUuid, dicomSeries))
+      if (HasSeries(seriesUuid, hasher.GetSeriesUid()))
       {
         // TODO: Check consistency?
       }
       else
       {
-        seriesUuid = CreateSeries(studyUuid, dicomSeries, dicomSummary);
+        seriesUuid = CreateSeries(studyUuid, hasher.GetSeriesUid(), dicomSummary);
       }
 
-      instanceUuid = CreateInstance(seriesUuid, dicomInstance, dicomSummary, fileUuid, 
+      instanceUuid = CreateInstance(seriesUuid, hasher.GetInstanceUid(), dicomSummary, fileUuid, 
                                     uncompressedFileSize, jsonUuid, distantAet);
       
       t.Commit();

--- a/OrthancServer/main.cpp	Fri Nov 09 10:42:00 2012 +0100
+++ b/OrthancServer/main.cpp	Fri Nov 09 11:13:29 2012 +0100
@@ -249,8 +249,8 @@
         httpServer.SetSslEnabled(false);
       }
 
-      LOG(INFO) << "DICOM server listening on port: " << dicomServer.GetPortNumber();
-      LOG(INFO) << "HTTP server listening on port: " << httpServer.GetPortNumber();
+      LOG(WARNING) << "DICOM server listening on port: " << dicomServer.GetPortNumber();
+      LOG(WARNING) << "HTTP server listening on port: " << httpServer.GetPortNumber();
 
 #if ORTHANC_STANDALONE == 1
       httpServer.RegisterHandler(new EmbeddedResourceHttpHandler("/app", EmbeddedResources::ORTHANC_EXPLORER));