occ_curve25519.h 3.8 KB

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  1. /**
  2. * Copyright (c) 2016 - 2019, Nordic Semiconductor ASA
  3. *
  4. * All rights reserved.
  5. *
  6. * Redistribution and use in source and binary forms, with or without modification,
  7. * are permitted provided that the following conditions are met:
  8. *
  9. * 1. Redistributions of source code must retain the above copyright notice, this
  10. * list of conditions and the following disclaimer.
  11. *
  12. * 2. Redistributions in binary form, except as embedded into a Nordic
  13. * Semiconductor ASA integrated circuit in a product or a software update for
  14. * such product, must reproduce the above copyright notice, this list of
  15. * conditions and the following disclaimer in the documentation and/or other
  16. * materials provided with the distribution.
  17. *
  18. * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
  19. * contributors may be used to endorse or promote products derived from this
  20. * software without specific prior written permission.
  21. *
  22. * 4. This software, with or without modification, must only be used with a
  23. * Nordic Semiconductor ASA integrated circuit.
  24. *
  25. * 5. Any software provided in binary form under this license must not be reverse
  26. * engineered, decompiled, modified and/or disassembled.
  27. *
  28. * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
  29. * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  30. * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
  31. * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
  32. * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  33. * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  34. * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  35. * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36. * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  37. * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  38. *
  39. */
  40. /**@file
  41. * Curve25519 is an elliptic curve offering 128 bits of security. It is designed
  42. * for use in the elliptic curve Diffie-Hellman (ECDH) key agreement scheme.
  43. *
  44. * @see [RFC 7748 - Elliptic Curves for Security](https://tools.ietf.org/html/rfc7748)
  45. * @see [Curve25519: high-speed elliptic-curve cryptography](http://cr.yp.to/ecdh.html)
  46. */
  47. #ifndef OCC_CURVE25519_H
  48. #define OCC_CURVE25519_H
  49. #include <stdint.h>
  50. /**
  51. * Length of a scalar.
  52. */
  53. #define occ_curve25519_SCALAR_BYTES (32)
  54. /**
  55. * Length of a curve point.
  56. */
  57. #define occ_curve25519_BYTES (32)
  58. /**
  59. * Curve25519 scalar multiplication `r = n * basePoint`.
  60. *
  61. * Given a secret key @p n, the corresponding Curve25519 public key is computed
  62. * and put into @p r.
  63. *
  64. * The inverse of this function is difficult to compute.
  65. *
  66. * **Example**
  67. * @include occ_curve25519_scalarmult_base.c
  68. *
  69. * @param[out] r Resulting curve point.
  70. * @param[in] n Scalar factor.
  71. *
  72. * @remark @p r and @p n can point to the same address.
  73. */
  74. void occ_curve25519_scalarmult_base(uint8_t r[occ_curve25519_BYTES],
  75. const uint8_t n[occ_curve25519_SCALAR_BYTES]);
  76. /**
  77. * Curve25519 scalar multiplication `r = n * p`.
  78. *
  79. * A shared secret is computed from the local secret key @p n and another
  80. * party's public key @p p and put into @p r. The same shared secret is
  81. * generated when the other party combines its private key with the local public
  82. * key.
  83. *
  84. * **Example**
  85. * @include occ_curve25519_scalarmult.c
  86. *
  87. * @param[out] r Resulting curve point.
  88. * @param[in] n Scalar factor.
  89. * @param[in] p Point factor.
  90. *
  91. * @remark @p r and @p n can point to the same address.
  92. */
  93. void occ_curve25519_scalarmult(uint8_t r[occ_curve25519_BYTES],
  94. const uint8_t n[occ_curve25519_SCALAR_BYTES],
  95. const uint8_t p[occ_curve25519_BYTES]);
  96. #endif