1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * Diffie-Hellman secret to be used with kpp API along with helper functions
4 *
5 * Copyright (c) 2016, Intel Corporation
6 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
7 */
8 #ifndef _CRYPTO_DH_
9 #define _CRYPTO_DH_
10
11 /**
12 * DOC: DH Helper Functions
13 *
14 * To use DH with the KPP cipher API, the following data structure and
15 * functions should be used.
16 *
17 * To use DH with KPP, the following functions should be used to operate on
18 * a DH private key. The packet private key that can be set with
19 * the KPP API function call of crypto_kpp_set_secret.
20 */
21
22 /**
23 * struct dh - define a DH private key
24 *
25 * @key: Private DH key
26 * @p: Diffie-Hellman parameter P
27 * @q: Diffie-Hellman parameter Q
28 * @g: Diffie-Hellman generator G
29 * @key_size: Size of the private DH key
30 * @p_size: Size of DH parameter P
31 * @q_size: Size of DH parameter Q
32 * @g_size: Size of DH generator G
33 */
34 struct dh {
35 void *key;
36 void *p;
37 void *q;
38 void *g;
39 unsigned int key_size;
40 unsigned int p_size;
41 unsigned int q_size;
42 unsigned int g_size;
43 };
44
45 /**
46 * crypto_dh_key_len() - Obtain the size of the private DH key
47 * @params: private DH key
48 *
49 * This function returns the packet DH key size. A caller can use that
50 * with the provided DH private key reference to obtain the required
51 * memory size to hold a packet key.
52 *
53 * Return: size of the key in bytes
54 */
55 unsigned int crypto_dh_key_len(const struct dh *params);
56
57 /**
58 * crypto_dh_encode_key() - encode the private key
59 * @buf: Buffer allocated by the caller to hold the packet DH
60 * private key. The buffer should be at least crypto_dh_key_len
61 * bytes in size.
62 * @len: Length of the packet private key buffer
63 * @params: Buffer with the caller-specified private key
64 *
65 * The DH implementations operate on a packet representation of the private
66 * key.
67 *
68 * Return: -EINVAL if buffer has insufficient size, 0 on success
69 */
70 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params);
71
72 /**
73 * crypto_dh_decode_key() - decode a private key
74 * @buf: Buffer holding a packet key that should be decoded
75 * @len: Length of the packet private key buffer
76 * @params: Buffer allocated by the caller that is filled with the
77 * unpacked DH private key.
78 *
79 * The unpacking obtains the private key by pointing @p to the correct location
80 * in @buf. Thus, both pointers refer to the same memory.
81 *
82 * Return: -EINVAL if buffer has insufficient size, 0 on success
83 */
84 int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params);
85
86 #endif
87
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