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ZcashFoundation / zcash-fpga

Zcash FPGA acceleration engine
GNU General Public License v3.0
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math calculate question #14

Closed Jiahua-Gong closed 4 years ago

Jiahua-Gong commented 4 years ago

I view the secp256k1 module.the ECDSA signature verification as follows

  1. compute w= s^(-1) mod n.
  2. u1=H(m)w mod n and u2 = rw mod n.
  3. X=u1P + u2Q.
  4. Covert the x-coordinate x1 of X to an integer /x1;compute v = /x1 mod n.

When the code compute X=u1P +u2Q.Using the Jacobian coordinate point add.Then I noticed you provide two ways (one is CALC_X_AFFINE,another is CHECK_IN_JB) to check the result.In the CALC_X_AFFINE state,Firstly mult the z^2 ,Secondly ,do the binary inverse . and inv_p is secp256k1_pkg::p_eq; I'm confused about the binary inverse.Thirdly, mult the z^2 with X to covert AFFINE .

I'm confused about CALC_X_AFFINE state operation.Could you explain to me? Thanks a lot.

Jiahua-Gong commented 4 years ago

I understand this code.