Point addition, P + Q = R, is defined as the reflection through the x-axis of the third intersecting point R’ on a line that includes P and Q.

Point doubling, P + P = R is defined by finding the line tangent to the point to be doubled, P, and taking reflection through the x-axis of the intersecting point R’ on the curve to get R.

For other coins was used

PrivatKey to WIF:

for BTC: Privatkey[0] = Convert.ToByte(128),

for example for NYC: Privatkey[0] = Convert.ToByte(188), etc...

Public to WalletAdress:

for BTC: sha256RIPEMD160publicKey[0] = Convert.ToByte(0),

for example for NYC: sha256RIPEMD160publicKey[0] = Convert.ToByte(60), etc...