diff options
Diffstat (limited to 'crypto/ec/ecp_nistp224.c')
| -rw-r--r-- | crypto/ec/ecp_nistp224.c | 33 |
1 files changed, 22 insertions, 11 deletions
diff --git a/crypto/ec/ecp_nistp224.c b/crypto/ec/ecp_nistp224.c index bf8021c6cf..4c76827db8 100644 --- a/crypto/ec/ecp_nistp224.c +++ b/crypto/ec/ecp_nistp224.c @@ -46,7 +46,8 @@ typedef int64_t s64; /******************************************************************************/ -/* INTERNAL REPRESENTATION OF FIELD ELEMENTS +/*- + * INTERNAL REPRESENTATION OF FIELD ELEMENTS * * Field elements are represented as a_0 + 2^56*a_1 + 2^112*a_2 + 2^168*a_3 * using 64-bit coefficients called 'limbs', @@ -94,7 +95,8 @@ static const felem_bytearray nistp224_curve_params[5] = { 0x44,0xd5,0x81,0x99,0x85,0x00,0x7e,0x34} }; -/* Precomputed multiples of the standard generator +/*- + * Precomputed multiples of the standard generator * Points are given in coordinates (X, Y, Z) where Z normally is 1 * (0 for the point at infinity). * For each field element, slice a_0 is word 0, etc. @@ -573,9 +575,11 @@ static void felem_reduce(felem out, const widefelem in) /* output[3] <= 2^56 + 2^16 */ out[2] = output[2] & 0x00ffffffffffffff; - /* out[0] < 2^56, out[1] < 2^56, out[2] < 2^56, + /*- + * out[0] < 2^56, out[1] < 2^56, out[2] < 2^56, * out[3] <= 2^56 + 2^16 (due to final carry), - * so out < 2*p */ + * so out < 2*p + */ out[3] = output[3]; } @@ -752,13 +756,15 @@ copy_conditional(felem out, const felem in, limb icopy) * */ -/* Double an elliptic curve point: +/*- + * Double an elliptic curve point: * (X', Y', Z') = 2 * (X, Y, Z), where * X' = (3 * (X - Z^2) * (X + Z^2))^2 - 8 * X * Y^2 * Y' = 3 * (X - Z^2) * (X + Z^2) * (4 * X * Y^2 - X') - 8 * Y^2 * Z' = (Y + Z)^2 - Y^2 - Z^2 = 2 * Y * Z * Outputs can equal corresponding inputs, i.e., x_out == x_in is allowed, - * while x_out == y_in is not (maybe this works, but it's not tested). */ + * while x_out == y_in is not (maybe this works, but it's not tested). + */ static void point_double(felem x_out, felem y_out, felem z_out, const felem x_in, const felem y_in, const felem z_in) @@ -830,7 +836,8 @@ point_double(felem x_out, felem y_out, felem z_out, felem_reduce(y_out, tmp); } -/* Add two elliptic curve points: +/*- + * Add two elliptic curve points: * (X_1, Y_1, Z_1) + (X_2, Y_2, Z_2) = (X_3, Y_3, Z_3), where * X_3 = (Z_1^3 * Y_2 - Z_2^3 * Y_1)^2 - (Z_1^2 * X_2 - Z_2^2 * X_1)^3 - * 2 * Z_2^2 * X_1 * (Z_1^2 * X_2 - Z_2^2 * X_1)^2 @@ -968,8 +975,10 @@ static void point_add(felem x3, felem y3, felem z3, felem_scalar(ftmp5, 2); /* ftmp5[i] < 2 * 2^57 = 2^58 */ - /* x_out = (z1^3*y2 - z2^3*y1)^2 - (z1^2*x2 - z2^2*x1)^3 - - 2*z2^2*x1*(z1^2*x2 - z2^2*x1)^2 */ + /*- + * x_out = (z1^3*y2 - z2^3*y1)^2 - (z1^2*x2 - z2^2*x1)^3 - + * 2*z2^2*x1*(z1^2*x2 - z2^2*x1)^2 + */ felem_diff_128_64(tmp2, ftmp5); /* tmp2[i] < 2^117 + 2^64 + 8 < 2^118 */ felem_reduce(x_out, tmp2); @@ -982,8 +991,10 @@ static void point_add(felem x3, felem y3, felem z3, felem_mul(tmp2, ftmp3, ftmp2); /* tmp2[i] < 4 * 2^57 * 2^59 = 2^118 */ - /* y_out = (z1^3*y2 - z2^3*y1)*(z2^2*x1*(z1^2*x2 - z2^2*x1)^2 - x_out) - - z2^3*y1*(z1^2*x2 - z2^2*x1)^3 */ + /*- + * y_out = (z1^3*y2 - z2^3*y1)*(z2^2*x1*(z1^2*x2 - z2^2*x1)^2 - x_out) - + * z2^3*y1*(z1^2*x2 - z2^2*x1)^3 + */ widefelem_diff(tmp2, tmp); /* tmp2[i] < 2^118 + 2^120 < 2^121 */ felem_reduce(y_out, tmp2); |