Private key used for sec in tx signing?

[mshearer0]

In sign_input in tx.py why is the private and not public key used to generate the sec?

calculate the sec sec = private_key.point.sec()

[aniketambore]

why is the private and not public key used to generate the sec?

We will be generating public_key from the private_key :). The purpose of passing private_key in sign_input is because we want to generate the der signature by signing z.

Also, the PrivateKey class in ecc.py is the one where we've the access of sec from the sec() method of S256Point.

Also, if you check the Exercise 1 of chapter 4 , we'd used private_key only, to find the uncompressed sec format.

That's the correct way of generating sec public key.

Thank you.

[mshearer0]

Many thanks @aniketambore

I’d missed the fact that the point initialised in the private key class is actually the public key:

def init(self, secret): self.secret = secret self.point = secret * G