1 /*
2 * Copyright (c) 2013, Kenneth MacKay
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
15 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
16 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
17 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
18 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
19 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
20 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26 #ifndef _CRYPTO_ECC_H
27 #define _CRYPTO_ECC_H
28
29 /* One digit is u64 qword. */
30 #define ECC_CURVE_NIST_P192_DIGITS 3
31 #define ECC_CURVE_NIST_P256_DIGITS 4
32 #define ECC_MAX_DIGITS (512 / 64)
33
34 #define ECC_DIGITS_TO_BYTES_SHIFT 3
35
36 /**
37 * struct ecc_point - elliptic curve point in affine coordinates
38 *
39 * @x: X coordinate in vli form.
40 * @y: Y coordinate in vli form.
41 * @ndigits: Length of vlis in u64 qwords.
42 */
43 struct ecc_point {
44 u64 *x;
45 u64 *y;
46 u8 ndigits;
47 };
48
49 #define ECC_POINT_INIT(x, y, ndigits) (struct ecc_point) { x, y, ndigits }
50
51 /**
52 * struct ecc_curve - definition of elliptic curve
53 *
54 * @name: Short name of the curve.
55 * @g: Generator point of the curve.
56 * @p: Prime number, if Barrett's reduction is used for this curve
57 * pre-calculated value 'mu' is appended to the @p after ndigits.
58 * Use of Barrett's reduction is heuristically determined in
59 * vli_mmod_fast().
60 * @n: Order of the curve group.
61 * @a: Curve parameter a.
62 * @b: Curve parameter b.
63 */
64 struct ecc_curve {
65 char *name;
66 struct ecc_point g;
67 u64 *p;
68 u64 *n;
69 u64 *a;
70 u64 *b;
71 };
72
73 /**
74 * ecc_is_key_valid() - Validate a given ECDH private key
75 *
76 * @curve_id: id representing the curve to use
77 * @ndigits: curve's number of digits
78 * @private_key: private key to be used for the given curve
79 * @private_key_len: private key length
80 *
81 * Returns 0 if the key is acceptable, a negative value otherwise
82 */
83 int ecc_is_key_valid(unsigned int curve_id, unsigned int ndigits,
84 const u64 *private_key, unsigned int private_key_len);
85
86 /**
87 * ecc_gen_privkey() - Generates an ECC private key.
88 * The private key is a random integer in the range 0 < random < n, where n is a
89 * prime that is the order of the cyclic subgroup generated by the distinguished
90 * point G.
91 * @curve_id: id representing the curve to use
92 * @ndigits: curve number of digits
93 * @private_key: buffer for storing the generated private key
94 *
95 * Returns 0 if the private key was generated successfully, a negative value
96 * if an error occurred.
97 */
98 int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey);
99
100 /**
101 * ecc_make_pub_key() - Compute an ECC public key
102 *
103 * @curve_id: id representing the curve to use
104 * @ndigits: curve's number of digits
105 * @private_key: pregenerated private key for the given curve
106 * @public_key: buffer for storing the generated public key
107 *
108 * Returns 0 if the public key was generated successfully, a negative value
109 * if an error occurred.
110 */
111 int ecc_make_pub_key(const unsigned int curve_id, unsigned int ndigits,
112 const u64 *private_key, u64 *public_key);
113
114 /**
115 * crypto_ecdh_shared_secret() - Compute a shared secret
116 *
117 * @curve_id: id representing the curve to use
118 * @ndigits: curve's number of digits
119 * @private_key: private key of part A
120 * @public_key: public key of counterpart B
121 * @secret: buffer for storing the calculated shared secret
122 *
123 * Note: It is recommended that you hash the result of crypto_ecdh_shared_secret
124 * before using it for symmetric encryption or HMAC.
125 *
126 * Returns 0 if the shared secret was generated successfully, a negative value
127 * if an error occurred.
128 */
129 int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
130 const u64 *private_key, const u64 *public_key,
131 u64 *secret);
132
133 /**
134 * ecc_is_pubkey_valid_partial() - Partial public key validation
135 *
136 * @curve: elliptic curve domain parameters
137 * @pk: public key as a point
138 *
139 * Valdiate public key according to SP800-56A section 5.6.2.3.4 ECC Partial
140 * Public-Key Validation Routine.
141 *
142 * Note: There is no check that the public key is in the correct elliptic curve
143 * subgroup.
144 *
145 * Return: 0 if validation is successful, -EINVAL if validation is failed.
146 */
147 int ecc_is_pubkey_valid_partial(const struct ecc_curve *curve,
148 struct ecc_point *pk);
149
150 /**
151 * vli_is_zero() - Determine is vli is zero
152 *
153 * @vli: vli to check.
154 * @ndigits: length of the @vli
155 */
156 bool vli_is_zero(const u64 *vli, unsigned int ndigits);
157
158 /**
159 * vli_cmp() - compare left and right vlis
160 *
161 * @left: vli
162 * @right: vli
163 * @ndigits: length of both vlis
164 *
165 * Returns sign of @left - @right, i.e. -1 if @left < @right,
166 * 0 if @left == @right, 1 if @left > @right.
167 */
168 int vli_cmp(const u64 *left, const u64 *right, unsigned int ndigits);
169
170 /**
171 * vli_sub() - Subtracts right from left
172 *
173 * @result: where to write result
174 * @left: vli
175 * @right vli
176 * @ndigits: length of all vlis
177 *
178 * Note: can modify in-place.
179 *
180 * Return: carry bit.
181 */
182 u64 vli_sub(u64 *result, const u64 *left, const u64 *right,
183 unsigned int ndigits);
184
185 /**
186 * vli_from_be64() - Load vli from big-endian u64 array
187 *
188 * @dest: destination vli
189 * @src: source array of u64 BE values
190 * @ndigits: length of both vli and array
191 */
192 void vli_from_be64(u64 *dest, const void *src, unsigned int ndigits);
193
194 /**
195 * vli_from_le64() - Load vli from little-endian u64 array
196 *
197 * @dest: destination vli
198 * @src: source array of u64 LE values
199 * @ndigits: length of both vli and array
200 */
201 void vli_from_le64(u64 *dest, const void *src, unsigned int ndigits);
202
203 /**
204 * vli_mod_inv() - Modular inversion
205 *
206 * @result: where to write vli number
207 * @input: vli value to operate on
208 * @mod: modulus
209 * @ndigits: length of all vlis
210 */
211 void vli_mod_inv(u64 *result, const u64 *input, const u64 *mod,
212 unsigned int ndigits);
213
214 /**
215 * vli_mod_mult_slow() - Modular multiplication
216 *
217 * @result: where to write result value
218 * @left: vli number to multiply with @right
219 * @right: vli number to multiply with @left
220 * @mod: modulus
221 * @ndigits: length of all vlis
222 *
223 * Note: Assumes that mod is big enough curve order.
224 */
225 void vli_mod_mult_slow(u64 *result, const u64 *left, const u64 *right,
226 const u64 *mod, unsigned int ndigits);
227
228 /**
229 * ecc_point_mult_shamir() - Add two points multiplied by scalars
230 *
231 * @result: resulting point
232 * @x: scalar to multiply with @p
233 * @p: point to multiply with @x
234 * @y: scalar to multiply with @q
235 * @q: point to multiply with @y
236 * @curve: curve
237 *
238 * Returns result = x * p + x * q over the curve.
239 * This works faster than two multiplications and addition.
240 */
241 void ecc_point_mult_shamir(const struct ecc_point *result,
242 const u64 *x, const struct ecc_point *p,
243 const u64 *y, const struct ecc_point *q,
244 const struct ecc_curve *curve);
245 #endif