def ext_pubkey
      k = ExtPubkey.new
      k.depth = depth
      k.number = number
      k.parent_fingerprint = parent_fingerprint
      k.chain_code = chain_code
      k.pubkey = key.pubkey
      k.ver = priv_ver_to_pub_ver
      k
    end
def ext_pubkey
      k = ExtPubkey.new
      k.depth = depth
      k.number = number
      k.parent_fingerprint = parent_fingerprint
      k.chain_code = chain_code
      k.pubkey = key.pubkey
      k.ver = priv_ver_to_pub_ver
      k
    end
get ExtPubkey from priv_key