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diff --git a/src/libipsec/esp_context.h b/src/libipsec/esp_context.h
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+/*
+ * Copyright (C) 2012 Tobias Brunner
+ * Copyright (C) 2012 Giuliano Grassi
+ * Copyright (C) 2012 Ralf Sager
+ * Hochschule fuer Technik Rapperswil
+ *
+ * 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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.
+ */
+
+/**
+ * @defgroup esp_context esp_context
+ * @{ @ingroup libipsec
+ */
+
+#ifndef ESP_CONTEXT_H_
+#define ESP_CONTEXT_H_
+
+#include <library.h>
+#include <crypto/crypters/crypter.h>
+#include <crypto/signers/signer.h>
+
+typedef struct esp_context_t esp_context_t;
+
+/**
+ *  ESP context, handles sequence numbers and maintains cryptographic primitives
+ */
+struct esp_context_t {
+
+	/**
+	 * Get the crypter.
+	 *
+	 * @return				crypter
+	 */
+	crypter_t *(*get_crypter)(esp_context_t *this);
+
+	/**
+	 * Get the signer.
+	 *
+	 * @return				signer
+	 */
+	signer_t *(*get_signer)(esp_context_t *this);
+
+	/**
+	 * Get the current outbound ESP sequence number or the highest authenticated
+	 * inbound sequence number.
+	 *
+	 * @return			current sequence number, in host byte order
+	 */
+	u_int32_t (*get_seqno)(esp_context_t *this);
+
+	/**
+	 * Allocate the next outbound ESP sequence number.
+	 *
+	 * @param seqno		the sequence number, in host byte order
+	 * @return			FALSE if the sequence number cycled or inbound context
+	 */
+	bool (*next_seqno)(esp_context_t *this, u_int32_t *seqno);
+
+	/**
+	 * Verify an ESP sequence number.  Checks whether a packet with this
+	 * sequence number was already received, using the anti-replay window.
+	 * This operation does not modify the internal state.  After the sequence
+	 * number is successfully verified and the ESP packet is authenticated,
+	 * set_authenticated_seqno() should be called.
+	 *
+	 * @param seqno		the sequence number to verify, in host byte order
+	 * @return			TRUE when sequence number is valid
+	 */
+	bool (*verify_seqno)(esp_context_t *this, u_int32_t seqno);
+
+	/**
+	 * Adds a sequence number that was successfully verified and
+	 * authenticated.  A user MUST call verify_seqno() immediately before
+	 * calling this method.
+	 *
+	 * @param seqno		verified and authenticated seq number in host byte order
+	 */
+	void (*set_authenticated_seqno)(esp_context_t *this,
+									u_int32_t seqno);
+
+	/**
+	 * Destroy an esp_context_t
+	 */
+	void (*destroy)(esp_context_t *this);
+
+};
+
+/**
+ * Create an esp_context_t instance
+ *
+ * @param enc_alg		encryption algorithm
+ * @param enc_key		encryption key
+ * @param int_alg		integrity protection algorithm
+ * @param int_key		integrity protection key
+ * @param inbound		TRUE to create an inbound ESP context
+ * @return				ESP context instance, or NULL if creation fails
+ */
+esp_context_t *esp_context_create(int enc_alg, chunk_t enc_key, int int_alg,
+								  chunk_t int_key, bool inbound);
+
+#endif /** ESP_CONTEXT_H_ @}*/
+