diff --git a/internals.h b/internals.h
new file mode 100644
index 0000000..32080ec
--- /dev/null
+++ b/internals.h
@@ -0,0 +1,46 @@
+/* This file is part of libbrandt.
+ * Copyright (C) 2016 GNUnet e.V.
+ *
+ * libbrandt 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.
+ *
+ * libbrandt 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
+ * libbrandt.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * @file internals.h
+ * @brief This header contains library internal structs.
+ */
+
+#ifndef _BRANDT_INTERNALS_H
+#define _BRANDT_INTERNALS_H
+
+#include <pari/pari.h>
+
+struct AuctionData {
+	GEN p; /** The "safe prime" p */
+	GEN q; /** The prime @f$q = (p - 1) / 2@f$. */
+	GEN g; /** The generator of @f$\mathbb{G}_q@f$ */
+	uint16_t n; /** The amount of bidders/agents */
+	uint16_t k; /** The amount of possible prices */
+
+	GEN x; /** Own private additive key share */
+	GEN y; /** Own public multiplicative key share */
+	GEN Y; /** Shared public key */
+
+	GEN m; /** Additive share of random exponents, type: Matrix(n,k) */
+	GEN r; /** Key share exponent, type: Vector(k) */
+	GEN b; /** Own bid, type: Vector(k) */
+
+	GEN alpha; /** Own alpha, type: Vector(k) */
+	GEN beta; /** Own beta, type: Vector(k) */
+};
+
+#endif
diff --git a/smc.c b/smc.c
index e3e90cf..02dfafc 100644
--- a/smc.c
+++ b/smc.c
@@ -19,27 +19,71 @@
  * @brief Implementation of the smc primitives.
  */
 
+#include "util.h"
+
 #include <pari/pari.h>
 
 GEN
 smc_hextodec (char *s)                      /* int */
 {
-	unsigned int i, tmp;
+	size_t i;
+	char c;
+	pari_sp ltop = avma;
 	GEN ret = gen_0;                        /* int */
-	GEN v = gtovecsmall (strtoGENstr (s));  /* vecsmall */
 
-	for (i = 1; i < lg (v); ++i)
+	for (i = 0; i < strlen (s); i++)
 	{
-		///TODO: scanf instead of if
-		if ((v[i] >= '0') && (v[i] <= '9'))
-			tmp = v[i] - '0';
-		else if ((v[i] >= 'a') && (v[i] <= 'f'))
-			tmp = v[i] + 10 - 'a';
-		else if ((v[i] >= 'A') && (v[i] <= 'F'))
-			tmp = v[i] + 10 - 'A';
-		else
-			pari_err (e_MISC, "invalid input format");
-		ret = addis (shifti (ret, 4), tmp);
+		errno = 0;
+		if (1 != sscanf (&s[i], "%1hhx", &c))
+		{
+			brandt_eprintf ("failed to parse hex (\"%s\") to decimal:", s);
+			return NULL;
+		}
+		ret = addis (shifti (ret, 4), c);
 	}
-	return ret;
+	return gerepilecopy (ltop, ret);
 }
+
+
+void
+smc_genbid (AuctionData *ad, uint16_t bid)
+{
+	uint16_t j;
+	pari_sp ltop = avma;
+	GEN ret = cgetg (itos (ad->k)+1, t_VEC);         /* vec */
+
+	for (j = 1; j <= ad->k; j++)
+	{
+		gel (ret, j) = gpowgs (ad->g, bid == j);
+	}
+	ad->b = gerepilecopy (ltop, ret);
+}
+
+void
+smc_genalpha (AuctionData *ad)
+{
+	uint16_t j;
+	pari_sp ltop = avma;
+	GEN ret = cgetg (ad->k+1, t_VEC);
+
+	for (j = 1; j <= ad->k; ++j)
+	{
+		gel (ret, j) = gmul (gel (ad->b, j), gpowgi (ad->y, gel (ad->r, j)));
+	}
+	ab->alpha = gerepilecopy (ltop, ret);
+}
+
+void
+smc_genbeta (AuctionData *ad)
+{
+	uint16_t j;
+	pari_sp ltop = avma;
+	GEN ret = cgetg (ad->k+1, t_VEC);
+
+	for (j = 1; j <= ad->k; ++j)
+	{
+		gel (ret, j) = gpowgi (ad->g, gel (ad->r, j));
+	}
+	ab->beta = gerepilecopy (ltop, ret);
+}
+
diff --git a/smc.gp b/smc.gp
index bc7b514..2b7e188 100644
--- a/smc.gp
+++ b/smc.gp
@@ -17,15 +17,19 @@ smc_hextodec(s:str) =
 	ret;
 }
 
-smc_genfield(p:int, g)=
+smc_genbid(k:small, bid:small, g)=
 {
-	local(q:int);
-	q = (p - 1) / 2;
-	[Mod(g^2, p), q];
+	vector(k,j,g^(bid==j));
 }
 
-smc_genkeypair(field:vec)=
+smc_genalpha(k:small, b:vec, r:vec, y)=
 {
-	local(x:int=random(field[2]));
-	[x, field[1]^x];
+	vector(k, j, b[j]*y^r[j]);
 }
+
+smc_genbeta(k:small, r:vec, g)=
+{
+	vector(k, j, g^r[j]);
+}
+
+
diff --git a/util.h b/util.h
new file mode 100644
index 0000000..f40dd36
--- /dev/null
+++ b/util.h
@@ -0,0 +1,25 @@
+/* This file is part of libgotr.
+ * (C) 2014-2015 Markus Teich, Jannik Theiß
+ *
+ * libgotr is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 3, or (at your
+ * option) any later version.
+ *
+ * libgotr 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with libgotr; see the file LICENSE.  If not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef _BRANDT_UTIL_H
+#define _BRANDT_UTIL_H
+
+void brandt_eprintf(const char *format, ...);
+
+#endif