Where should I look at in Bitcoin Core source code to figure out how the signature process trasform a message in a curve point?
To sign a transaction (message) in Bitcoin system, you need to encode the message to a point of the curve $y^2=x^3+7$. I read this Koblitz's paper. There are three encoding schemes. I read this question too.
If I look at in Bitcoin Core source code I can't see any of these encoding schemes, it seems to me that message $M$ is directly encoded in a point ($ \rightarrow hash(M) $) without check; obviously that is not possible, there is roughly a 50% chance that a random 256 bit string don't correspond to a point of the curve. I can't find out how/if the ECDSA library checks if $hash(M)$ is on the curve or not and especially what it does if the $hash(M)$ is not on the curve.
What encoding scheme does Bitcoin-ECDSA implement and where is it in the source code?
Thanks and sorry for my English.