diff --git a/include/grgsm/decryption/CMakeLists.txt b/include/grgsm/decryption/CMakeLists.txt
new file mode 100644
index 0000000..3a0c6b6
--- /dev/null
+++ b/include/grgsm/decryption/CMakeLists.txt
@@ -0,0 +1,25 @@
+# Copyright 2011,2012 Free Software Foundation, Inc.
+#
+# This file is part of GNU Radio
+#
+# GNU Radio 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, or (at your option)
+# any later version.
+#
+# GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+
+########################################################################
+# Install public header files
+########################################################################
+install(FILES
+    decryption.h DESTINATION include/grgsm/decoding
+)
diff --git a/include/grgsm/decryption/decryption.h b/include/grgsm/decryption/decryption.h
new file mode 100644
index 0000000..96d3eca
--- /dev/null
+++ b/include/grgsm/decryption/decryption.h
@@ -0,0 +1,60 @@
+/* -*- c++ -*- */
+/* 
+ *  @file
+ *  @author Piotr Krysik <ptrkrysik@gmail.com>
+ *  @section LICENSE
+ *  
+ *  Gr-gsm 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, or (at your option)
+ *  any later version.
+ *  
+ *  Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, Inc., 51 Franklin Street,
+ *  Boston, MA 02110-1301, USA.
+ * 
+ */
+
+
+#ifndef INCLUDED_GSM_DECRYPTION_H
+#define INCLUDED_GSM_DECRYPTION_H
+
+#include <grgsm/api.h>
+#include <gnuradio/block.h>
+
+namespace gr {
+  namespace gsm {
+
+    /*!
+     * \brief <+description of block+>
+     * \ingroup gsm
+     *
+     */
+    class GSM_API decryption : virtual public gr::block
+    {
+     public:
+      typedef boost::shared_ptr<decryption> sptr;
+
+      /*!
+       * \brief Return a shared_ptr to a new instance of gsm::decryption.
+       *
+       * To avoid accidental use of raw pointers, gsm::decryption's
+       * constructor is in a private implementation
+       * class. gsm::decryption::make is the public interface for
+       * creating new instances.
+       */
+      static sptr make(const std::vector<uint8_t> & k_c);
+      virtual void set_k_c(const std::vector<uint8_t> & k_c) = 0;
+    };
+
+  } // namespace gsm
+} // namespace gr
+
+#endif /* INCLUDED_GSM_DECRYPTION_H */
+