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