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