encoding/MAGIC

    MAGIC is an atom holding magic number/string aimed to identify the data
    following it. It is a concatenation of ASCII("KEKS") and 12-byte magic,
    padded with zeros if necessary. Zero bytes should not be used in it,
    except for trailing ones.

    It is intended to be prepended to the KEKS-encoded data in files.

    Example representations:

    MAGIC cm/pub       | 4B454B53 636D2F707562 000000000000
    MAGIC cm/signed    | 4B454B53 636D2F7369676E6564 000000
    MAGIC cm/encrypted | 4B454B53 636D2F656E63727970746564