diff --git a/include/polarssl/asn1write.h b/include/polarssl/asn1write.h
new file mode 100644
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--- /dev/null
+++ b/include/polarssl/asn1write.h
@@ -0,0 +1,46 @@
+/**
+ * \file asn1write.h
+ *
+ * \brief ASN.1 buffer writing functionality
+ *
+ *  Copyright (C) 2006-2012, Brainspark B.V.
+ *
+ *  This file is part of PolarSSL (http://www.polarssl.org)
+ *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
+ *
+ *  All rights reserved.
+ *
+ *  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 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  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, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#ifndef POLARSSL_ASN1_WRITE_H
+#define POLARSSL_ASN1_WRITE_H
+
+#include "asn1.h"
+
+#define POLARSSL_ERR_ASN1_BUF_TOO_SMALL                    -0x006C  /**< Buffer too small when writing ASN.1 data structure. */
+
+#define ASN1_CHK_ADD(g, f) if( ( ret = f ) < 0 ) return( ret ); else g += ret
+
+int asn1_write_len( unsigned char **p, unsigned char *start, size_t len );
+int asn1_write_tag( unsigned char **p, unsigned char *start, unsigned char tag );
+int asn1_write_mpi( unsigned char **p, unsigned char *start, mpi *X );
+int asn1_write_null( unsigned char **p, unsigned char *start );
+int asn1_write_oid( unsigned char **p, unsigned char *start, char *oid );
+int asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start, char *algorithm_oid );
+int asn1_write_int( unsigned char **p, unsigned char *start, int val );
+int asn1_write_printable_string( unsigned char **p, unsigned char *start,
+                                 char *text );
+
+#endif /* POLARSSL_ASN1_WRITE_H */