crypto/ecc.h

   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