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 */