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More optimisations for EC P-256 "i15" (specialised squaring function, mixed coordinates addition with a 4-bit window when the base point is the conventional generator).

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Thomas Pornin 2017-01-13 05:10:43 +01:00
parent 21743ae69e
commit 44c79c1add
14 changed files with 804 additions and 56 deletions
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35
inc/bearssl_ec.h
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@ -69,6 +69,11 @@
*
* Multiply a curve point with an integer.
*
* - `mulgen()`
*
* Multiply the curve generator with an integer. This may be faster
* than the generic `mul()`.
*
* - `muladd()`
*
* Multiply two curve points by two integers, and return the sum of
@ -299,10 +304,9 @@ typedef struct {
* not the case, then this function returns an error (0).
*
* - The multiplier integer MUST be non-zero and less than the
* curve subgroup order. If the integer is zero, then an
* error is reported, but if the integer is not lower than
* the subgroup order, then the result is indeterminate and an
* error code is not guaranteed.
* curve subgroup order. If this property does not hold, then
* the result is indeterminate and an error code is not
* guaranteed.
*
* Returned value is 1 on success, 0 on error. On error, the
* contents of `G` are indeterminate.
@ -317,6 +321,22 @@ typedef struct {
uint32_t (*mul)(unsigned char *G, size_t Glen,
const unsigned char *x, size_t xlen, int curve);
/**
* \brief Multiply the generator by an integer.
*
* The multiplier MUST be non-zero and less than the curve
* subgroup order. Results are indeterminate if this property
* does not hold.
*
* \param R output buffer for the point.
* \param x multiplier (unsigned big-endian).
* \param xlen multiplier length (in bytes).
* \param curve curve identifier.
* \return encoded result point length (in bytes).
*/
size_t (*mulgen)(unsigned char *R,
const unsigned char *x, size_t xlen, int curve);
/**
* \brief Multiply two points by two integers and add the
* results.
@ -333,6 +353,11 @@ typedef struct {
* infinity" either). If this is not the case, then this
* function returns an error (0).
*
* - If the `B` pointer is `NULL`, then the conventional
* subgroup generator is used. With some implementations,
* this may be faster than providing a pointer to the
* generator.
*
* - The multiplier integers (`x` and `y`) MUST be non-zero
* and less than the curve subgroup order. If either integer
* is zero, then an error is reported, but if one of them is
@ -346,7 +371,7 @@ typedef struct {
* contents of `A` are indeterminate.
*
* \param A first point to multiply.
* \param B second point to multiply.
* \param B second point to multiply (`NULL` for the generator).
* \param len common length of the encoded points (in bytes).
* \param x multiplier for `A` (unsigned big-endian).
* \param xlen length of multiplier for `A` (in bytes).