def public_key(format: :z85)
      case format
      when :z85
        ffi_delegate.public_txt.force_encoding(Encoding::ASCII)
      when :binary
        ffi_delegate.public_key.read_string(32)
      else
        raise ArgumentError, "invalid format: %p" % format
      end
    end
def public_key(format: :z85)
      case format
      when :z85
        ffi_delegate.public_txt.force_encoding(Encoding::ASCII)
      when :binary
        ffi_delegate.public_key.read_string(32)
      else
        raise ArgumentError, "invalid format: %p" % format
      end
    end
Initialize a new in-memory certificate with random keys.
 Returns the public key either as Z85-encoded ASCII string (default) or
 binary string.
 @param format [Symbol] +:z85+ for Z85, +:binary+ for binary
 @return [String] public key