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diff --git a/src/gsm/gea.c b/src/gsm/gea.c
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+/*
+ * gea.c
+ *
+ * Implementation of GEA3 and GEA4
+ *
+ * Copyright (C) 2016 by Sysmocom s.f.m.c. GmbH
+ *
+ * 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 3 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.
+ */
+
+#include <osmocom/core/bits.h>
+#include <osmocom/crypt/gprs_cipher.h>
+#include <osmocom/crypt/auth.h>
+#include <osmocom/gsm/kasumi.h>
+
+#include <stdint.h>
+#include <string.h>
+
+/*! \brief Performs the GEA4 algorithm as in 3GPP TS 55.226 V9.0.0
+ * \param[in,out] out Buffer for gamma for encrypted/decrypted
+ * \param[in] len Length of out, in bytes
+ * \param[in] kc Buffer with the ciphering key
+ * \param[in] iv Init vector
+ * \param[in] direct Direction: 0 (MS -> SGSN) or 1 (SGSN -> MS)
+ */
+int gea4(uint8_t *out, uint16_t len, uint8_t *kc, uint32_t iv,
+ enum gprs_cipher_direction direction)
+{
+ _kasumi_kgcore(0xFF, 0, iv, direction, kc, out, len * 8);
+ return 0;
+}
+
+/*! \brief Performs the GEA3 algorithm as in 3GPP TS 55.216 V6.2.0
+ * \param[in,out] out Buffer for gamma for encrypted/decrypted
+ * \param[in] len Length of out, in bytes
+ * \param[in] kc Buffer with the ciphering key
+ * \param[in] iv Init vector
+ * \param[in] direct Direction: 0 (MS -> SGSN) or 1 (SGSN -> MS)
+ */
+int gea3(uint8_t *out, uint16_t len, uint8_t *kc, uint32_t iv,
+ enum gprs_cipher_direction direction)
+{
+ uint8_t ck[gprs_cipher_key_length(GPRS_ALGO_GEA4)];
+ osmo_c4(ck, kc);
+ return gea4(out, len, ck, iv, direction);
+}