1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * ECDH params to be used with kpp API
4 *
5 * Copyright (c) 2016, Intel Corporation
6 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
7 */
8 #ifndef _CRYPTO_ECDH_
9 #define _CRYPTO_ECDH_
10
11 /**
12 * DOC: ECDH Helper Functions
13 *
14 * To use ECDH with the KPP cipher API, the following data structure and
15 * functions should be used.
16 *
17 * The ECC curves known to the ECDH implementation are specified in this
18 * header file.
19 *
20 * To use ECDH with KPP, the following functions should be used to operate on
21 * an ECDH private key. The packet private key that can be set with
22 * the KPP API function call of crypto_kpp_set_secret.
23 */
24
25 /* Curves IDs */
26 #define ECC_CURVE_NIST_P192 0x0001
27 #define ECC_CURVE_NIST_P256 0x0002
28
29 /**
30 * struct ecdh - define an ECDH private key
31 *
32 * @curve_id: ECC curve the key is based on.
33 * @key: Private ECDH key
34 * @key_size: Size of the private ECDH key
35 */
36 struct ecdh {
37 unsigned short curve_id;
38 char *key;
39 unsigned short key_size;
40 };
41
42 /**
43 * crypto_ecdh_key_len() - Obtain the size of the private ECDH key
44 * @params: private ECDH key
45 *
46 * This function returns the packet ECDH key size. A caller can use that
47 * with the provided ECDH private key reference to obtain the required
48 * memory size to hold a packet key.
49 *
50 * Return: size of the key in bytes
51 */
52 unsigned int crypto_ecdh_key_len(const struct ecdh *params);
53
54 /**
55 * crypto_ecdh_encode_key() - encode the private key
56 * @buf: Buffer allocated by the caller to hold the packet ECDH
57 * private key. The buffer should be at least crypto_ecdh_key_len
58 * bytes in size.
59 * @len: Length of the packet private key buffer
60 * @p: Buffer with the caller-specified private key
61 *
62 * The ECDH implementations operate on a packet representation of the private
63 * key.
64 *
65 * Return: -EINVAL if buffer has insufficient size, 0 on success
66 */
67 int crypto_ecdh_encode_key(char *buf, unsigned int len, const struct ecdh *p);
68
69 /**
70 * crypto_ecdh_decode_key() - decode a private key
71 * @buf: Buffer holding a packet key that should be decoded
72 * @len: Length of the packet private key buffer
73 * @p: Buffer allocated by the caller that is filled with the
74 * unpacked ECDH private key.
75 *
76 * The unpacking obtains the private key by pointing @p to the correct location
77 * in @buf. Thus, both pointers refer to the same memory.
78 *
79 * Return: -EINVAL if buffer has insufficient size, 0 on success
80 */
81 int crypto_ecdh_decode_key(const char *buf, unsigned int len, struct ecdh *p);
82
83 #endif