Private key generation

The parent key, chain code, and index number are combined and hashed with the HMAC-SHA512 algorithm to produce a 512-bit hash using the following formula:

I = HMAC-SHA512(Key = Cpar ,Data = serp (point(kpar )) || ser32 (i))

The resultant hash is split in two hashes, I_L and I_R The right-hand half of the hash output becomes the chain code for the child, and the left-hand half of the hash and its index number are used to produce the child private key as well as to derive the child public key.

By changing the index, we can create multiple child keys in the sequence.