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Add ECCPoint_mult_safer() function

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This avoids the need for each calling site to manually regularize the scalar
and randomize coordinates, which makes for simpler safe use and saves 50 bytes
of code size in the library.
This commit is contained in:
Manuel Pégourié-Gonnard 2019-11-04 11:19:30 +01:00
parent c78d86b499
commit ef238283d5
4 changed files with 61 additions and 49 deletions
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14
include/tinycrypt/ecc.h
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@ -309,6 +309,20 @@ void EccPoint_mult(uECC_word_t * result, const uECC_word_t * point,
const uECC_word_t * scalar, const uECC_word_t * initial_Z,
bitcount_t num_bits, uECC_Curve curve);
/*
* @brief Point multiplication algorithm using Montgomery's ladder with co-Z
* coordinates. See http://eprint.iacr.org/2011/338.pdf.
* Uses scalar regularization and coordinate randomization (if a global RNG
* function is set) in order to protect against some side channel attacks.
* @note Result may overlap point.
* @param result OUT -- returns scalar*point
* @param point IN -- elliptic curve point
* @param scalar IN -- scalar
* @param curve IN -- elliptic curve
*/
int EccPoint_mult_safer(uECC_word_t * result, const uECC_word_t * point,
const uECC_word_t * scalar, uECC_Curve curve);
/*
* @brief Constant-time comparison to zero - secure way to compare long integers
* @param vli IN -- very long integer