diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index 83f9dac..a124720 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -1312,6 +1312,20 @@
 //#define POLARSSL_HAVEGE_C
 
 /**
+ * \def POLARSSL_HMAC_DRBG_C
+ *
+ * Enable the HMAC_DRBG random generator.
+ *
+ * Module:  library/hmac_drbg.c
+ * Caller:
+ *
+ * Requires: POLARSSL_MD_C
+ *
+ * Uncomment to enable the HMAC_DRBG random number geerator.
+ */
+#define POLARSSL_HMAC_DRBG_C
+
+/**
  * \def POLARSSL_MD_C
  *
  * Enable the generic message digest layer.
@@ -2000,6 +2014,10 @@
 #error "POLARSSL_HAVEGE_C defined, but not all prerequisites"
 #endif
 
+#if defined(POLARSSL_HMAC_DRBG) && !defined(POLARSSL_MD_C)
+#error "POLARSSL_HMAC_DRBG_C defined, but not all prerequisites"
+#endif
+
 #if defined(POLARSSL_KEY_EXCHANGE_ECDH_ECDSA_ENABLED) &&                 \
     ( !defined(POLARSSL_ECDH_C) || !defined(POLARSSL_X509_CRT_PARSE_C) )
 #error "POLARSSL_KEY_EXCHANGE_ECDH_ECDSA_ENABLED defined, but not all prerequisites"
diff --git a/include/polarssl/hmac_drbg.h b/include/polarssl/hmac_drbg.h
new file mode 100644
index 0000000..f86c136
--- /dev/null
+++ b/include/polarssl/hmac_drbg.h
@@ -0,0 +1,112 @@
+/**
+ * \file hmac_drbg.h
+ *
+ * \brief HMAC_DRBG (NIST SP 800-90A)
+ *
+ *  Copyright (C) 2014, 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_HMAC_DRBG_H
+#define POLARSSL_HMAC_DRBG_H
+
+#include "md.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Simplified HMAC_DRBG context.
+ * No reseed counter, no prediction resistance flag.
+ */
+typedef struct
+{
+    md_context_t md_ctx;
+    unsigned char V[POLARSSL_MD_MAX_SIZE];
+    unsigned char K[POLARSSL_MD_MAX_SIZE];
+} hmac_drbg_context;
+
+/**
+ * \brief               HMAC_DRBG initialisation
+ *
+ * \param ctx           HMAC_DRBG context to be initialised
+ * \param md_info       MD algorithm to use for HMAC_DRBG
+ * \param data          Concatenation of entropy string and additional data
+ * \param data_len      Length of data in bytes
+ *
+ * \todo                Use entropy callback rather than buffer.
+ *
+ * \return              0 if successful, or
+ *                      POLARSSL_ERR_MD_BAD_INPUT_DATA, or
+ *                      POLARSSL_ERR_MD_ALLOC_FAILED
+ */
+int hmac_drbg_init( hmac_drbg_context *ctx,
+                    const md_info_t * md_info,
+                    const unsigned char *data, size_t data_len );
+
+/**
+ * \brief               HMAC_DRBG update state
+ *
+ * \param ctx           HMAC_DRBG context
+ * \param additional    Additional data to update state with, or NULL
+ * \param add_len       Length of additional data, or 0
+ *
+ * \note                Additional data is optional, pass NULL and 0 as second
+ *                      third argument if no additional data is being used.
+ */
+void hmac_drbg_update( hmac_drbg_context *ctx,
+                       const unsigned char *additional, size_t add_len );
+
+/**
+ * \brief               HMAC_DRBG generate random
+ *
+ * Note: Automatically reseeds if reseed_counter is reached. (TODO)
+ *
+ * \param p_rng         HMAC_DRBG context
+ * \param output        Buffer to fill
+ * \param output_len    Length of the buffer
+ *
+ * \return              0 if successful.
+ */
+int hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len );
+
+/**
+ * \brief               Free an HMAC_DRBG context
+ *
+ * \param ctx           HMAC_DRBG context to free.
+ */
+void hmac_drbg_free( hmac_drbg_context *ctx );
+
+
+#if defined(POLARSSL_SELF_TEST)
+/**
+ * \brief               Checkup routine
+ *
+ * \return              0 if successful, or 1 if the test failed
+ */
+int hmac_drbg_self_test( int verbose );
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* hmac_drbg.h */
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index dd6bbd3..77aac20 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -26,6 +26,7 @@
      error.c
      gcm.c
      havege.c
+     hmac_drbg.c
      md.c
      md_wrap.c
      md2.c
diff --git a/library/Makefile b/library/Makefile
index a4126f0..311e316 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -44,6 +44,7 @@
 		ecp.o		ecp_curves.o				\
 		entropy.o	entropy_poll.o				\
 		error.o		gcm.o		havege.o		\
+		hmac_drbg.o								\
 		md.o		md_wrap.o	md2.o			\
 		md4.o		md5.o		memory.o		\
 		memory_buffer_alloc.o	net.o			\
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
new file mode 100644
index 0000000..6aa1ba5
--- /dev/null
+++ b/library/hmac_drbg.c
@@ -0,0 +1,143 @@
+/*
+ *  HMAC_DRBG implementation (NIST SP 800-90)
+ *
+ *  Copyright (C) 2014, 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.
+ */
+
+/*
+ *  The NIST SP 800-90 DRBGs are described in the following publication.
+ *  http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf
+ */
+
+#include "polarssl/config.h"
+
+#if defined(POLARSSL_HMAC_DRBG_C)
+
+#include "polarssl/hmac_drbg.h"
+
+/*
+ * HMAC_DRBG update, using optional additional data
+ */
+void hmac_drbg_update( hmac_drbg_context *ctx,
+                       const unsigned char *additional, size_t add_len )
+{
+    size_t md_len = ctx->md_ctx.md_info->size;
+    unsigned char rounds = ( additional != NULL && add_len != 0 ) ? 2 : 1;
+    unsigned char sep[1];
+
+    for( sep[0] = 0; sep[0] < rounds; sep[0]++ )
+    {
+        md_hmac_starts( &ctx->md_ctx, ctx->K, md_len );
+        md_hmac_update( &ctx->md_ctx, ctx->V, md_len );
+        md_hmac_update( &ctx->md_ctx, sep, 1 );
+        if( rounds == 2 )
+            md_hmac_update( &ctx->md_ctx, additional, add_len );
+        md_hmac_finish( &ctx->md_ctx, ctx->K );
+
+        md_hmac_starts( &ctx->md_ctx, ctx->K, md_len );
+        md_hmac_update( &ctx->md_ctx, ctx->V, md_len );
+        md_hmac_finish( &ctx->md_ctx, ctx->V );
+    }
+}
+
+/*
+ * Simplified HMAC_DRBG initialisation.
+ */
+int hmac_drbg_init( hmac_drbg_context *ctx,
+                    const md_info_t * md_info,
+                    const unsigned char *data, size_t data_len )
+{
+    int ret;
+
+    memset( ctx, 0, sizeof( hmac_drbg_context ) );
+
+    if( ( ret = md_init_ctx( &ctx->md_ctx, md_info ) ) != 0 )
+        return( ret );
+
+    memset( ctx->V, 0x01, md_info->size );
+    /* ctx->K is already 0 */
+
+    hmac_drbg_update( ctx, data, data_len );
+
+    return( 0 );
+}
+
+/*
+ * Simplified HMAC_DRBG random function
+ */
+int hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len )
+{
+    hmac_drbg_context *ctx = (hmac_drbg_context *) p_rng;
+    size_t md_len = ctx->md_ctx.md_info->size;
+    size_t left = out_len;
+    unsigned char *out = output;
+
+    while( left != 0 )
+    {
+        size_t use_len = left > md_len ? md_len : left;
+
+        md_hmac_starts( &ctx->md_ctx, ctx->K, md_len );
+        md_hmac_update( &ctx->md_ctx, ctx->V, md_len );
+        md_hmac_finish( &ctx->md_ctx, ctx->V );
+
+        memcpy( out, ctx->V, use_len );
+        out += use_len;
+        left -= use_len;
+    }
+
+    hmac_drbg_update( ctx, NULL, 0 );
+
+    return( 0 );
+}
+
+/*
+ * Free an HMAC_DRBG context
+ */
+void hmac_drbg_free( hmac_drbg_context *ctx )
+{
+    if( ctx == NULL )
+        return;
+
+    md_free_ctx( &ctx->md_ctx );
+
+    memset( ctx, 0, sizeof( hmac_drbg_context ) );
+}
+
+
+#if defined(POLARSSL_SELF_TEST)
+
+#include <stdio.h>
+
+/*
+ * Checkup routine
+ */
+int hmac_drbg_self_test( int verbose )
+{
+
+    if( verbose != 0 )
+            printf( "\n" );
+
+    return( 0 );
+}
+#endif /* POLARSSL_SELF_TEST */
+
+#endif /* POLARSSL_HMAC_DRBG_C */
diff --git a/visualc/VS2010/PolarSSL.vcxproj b/visualc/VS2010/PolarSSL.vcxproj
index 127d106..84beb62 100644
--- a/visualc/VS2010/PolarSSL.vcxproj
+++ b/visualc/VS2010/PolarSSL.vcxproj
@@ -168,6 +168,7 @@
     <ClInclude Include="..\..\include\polarssl\error.h" />
     <ClInclude Include="..\..\include\polarssl\gcm.h" />
     <ClInclude Include="..\..\include\polarssl\havege.h" />
+    <ClInclude Include="..\..\include\polarssl\hmac_drbg.h" />
     <ClInclude Include="..\..\include\polarssl\md2.h" />
     <ClInclude Include="..\..\include\polarssl\md4.h" />
     <ClInclude Include="..\..\include\polarssl\md5.h" />
@@ -227,6 +228,7 @@
     <ClCompile Include="..\..\library\error.c" />
     <ClCompile Include="..\..\library\gcm.c" />
     <ClCompile Include="..\..\library\havege.c" />
+    <ClCompile Include="..\..\library\hmac_drbg.c" />
     <ClCompile Include="..\..\library\md2.c" />
     <ClCompile Include="..\..\library\md4.c" />
     <ClCompile Include="..\..\library\md5.c" />
diff --git a/visualc/VS6/polarssl.dsp b/visualc/VS6/polarssl.dsp
index 645b29c..f763caa 100644
--- a/visualc/VS6/polarssl.dsp
+++ b/visualc/VS6/polarssl.dsp
@@ -185,6 +185,10 @@
 # End Source File
 # Begin Source File
 
+SOURCE=..\..\library\hmac_drbg.c
+# End Source File
+# Begin Source File
+
 SOURCE=..\..\library\md2.c
 # End Source File
 # Begin Source File
@@ -457,6 +461,10 @@
 # End Source File
 # Begin Source File
 
+SOURCE=..\..\include\polarssl\hmac_drbg.h
+# End Source File
+# Begin Source File
+
 SOURCE=..\..\include\polarssl\md2.h
 # End Source File
 # Begin Source File