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+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * ECDH params to be used with kpp API
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
+ */
+#ifndef _CRYPTO_ECDH_
+#define _CRYPTO_ECDH_
+
+/**
+ * DOC: ECDH Helper Functions
+ *
+ * To use ECDH with the KPP cipher API, the following data structure and
+ * functions should be used.
+ *
+ * The ECC curves known to the ECDH implementation are specified in this
+ * header file.
+ *
+ * To use ECDH with KPP, the following functions should be used to operate on
+ * an ECDH private key. The packet private key that can be set with
+ * the KPP API function call of crypto_kpp_set_secret.
+ */
+
+/* Curves IDs */
+#define ECC_CURVE_NIST_P192 0x0001
+#define ECC_CURVE_NIST_P256 0x0002
+#define ECC_CURVE_NIST_P384 0x0003
+
+/**
+ * struct ecdh - define an ECDH private key
+ *
+ * @key: Private ECDH key
+ * @key_size: Size of the private ECDH key
+ */
+struct ecdh {
+ char *key;
+ unsigned short key_size;
+};
+
+/**
+ * crypto_ecdh_key_len() - Obtain the size of the private ECDH key
+ * @params: private ECDH key
+ *
+ * This function returns the packet ECDH key size. A caller can use that
+ * with the provided ECDH private key reference to obtain the required
+ * memory size to hold a packet key.
+ *
+ * Return: size of the key in bytes
+ */
+unsigned int crypto_ecdh_key_len(const struct ecdh *params);
+
+/**
+ * crypto_ecdh_encode_key() - encode the private key
+ * @buf: Buffer allocated by the caller to hold the packet ECDH
+ * private key. The buffer should be at least crypto_ecdh_key_len
+ * bytes in size.
+ * @len: Length of the packet private key buffer
+ * @p: Buffer with the caller-specified private key
+ *
+ * The ECDH implementations operate on a packet representation of the private
+ * key.
+ *
+ * Return: -EINVAL if buffer has insufficient size, 0 on success
+ */
+int crypto_ecdh_encode_key(char *buf, unsigned int len, const struct ecdh *p);
+
+/**
+ * crypto_ecdh_decode_key() - decode a private key
+ * @buf: Buffer holding a packet key that should be decoded
+ * @len: Length of the packet private key buffer
+ * @p: Buffer allocated by the caller that is filled with the
+ * unpacked ECDH private key.
+ *
+ * The unpacking obtains the private key by pointing @p to the correct location
+ * in @buf. Thus, both pointers refer to the same memory.
+ *
+ * Return: -EINVAL if buffer has insufficient size, 0 on success
+ */
+int crypto_ecdh_decode_key(const char *buf, unsigned int len, struct ecdh *p);
+
+#endif