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 * @g: Diffie-Hellman generator G
28 * @key_size: Size of the private DH key
29 * @p_size: Size of DH parameter P
30 * @g_size: Size of DH generator G
31 */
32 struct dh {
33 const void *key;
34 const void *p;
35 const void *g;
36 unsigned int key_size;
37 unsigned int p_size;
38 unsigned int g_size;
39 };
40
41 /**
42 * crypto_dh_key_len() - Obtain the size of the private DH key
43 * @params: private DH key
44 *
45 * This function returns the packet DH key size. A caller can use that
46 * with the provided DH private key reference to obtain the required
47 * memory size to hold a packet key.
48 *
49 * Return: size of the key in bytes
50 */
51 unsigned int crypto_dh_key_len(const struct dh *params);
52
53 /**
54 * crypto_dh_encode_key() - encode the private key
55 * @buf: Buffer allocated by the caller to hold the packet DH
56 * private key. The buffer should be at least crypto_dh_key_len
57 * bytes in size.
58 * @len: Length of the packet private key buffer
59 * @params: Buffer with the caller-specified private key
60 *
61 * The DH implementations operate on a packet representation of the private
62 * key.
63 *
64 * Return: -EINVAL if buffer has insufficient size, 0 on success
65 */
66 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params);
67
68 /**
69 * crypto_dh_decode_key() - decode a private key
70 * @buf: Buffer holding a packet key that should be decoded
71 * @len: Length of the packet private key buffer
72 * @params: Buffer allocated by the caller that is filled with the
73 * unpacked DH private key.
74 *
75 * The unpacking obtains the private key by pointing @p to the correct location
76 * in @buf. Thus, both pointers refer to the same memory.
77 *
78 * Return: -EINVAL if buffer has insufficient size, 0 on success
79 */
80 int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params);
81
82 /**
83 * __crypto_dh_decode_key() - decode a private key without parameter checks
84 * @buf: Buffer holding a packet key that should be decoded
85 * @len: Length of the packet private key buffer
86 * @params: Buffer allocated by the caller that is filled with the
87 * unpacked DH private key.
88 *
89 * Internal function providing the same services as the exported
90 * crypto_dh_decode_key(), but without any of those basic parameter
91 * checks conducted by the latter.
92 *
93 * Return: -EINVAL if buffer has insufficient size, 0 on success
94 */
95 int __crypto_dh_decode_key(const char *buf, unsigned int len,
96 struct dh *params);
97
98 #endif
99
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