Usage:  key child DERIVATION-PATH

  Derive child keys from a parent public/private key

Available options:
  -h,--help                Show this help text
  DERIVATION-PATH          Slash-separated derivation path.
                           Hardened indexes are marked with a 'H'
                           (e.g. 1852H/1815H/0H/0).

The parent key is read from stdin.
