This holds the first of eight possible 192-bit Triple DES transmit encryption keys, entered as a 48-character hex string. Having eight selectable keys rather than just one lets the modem rotate which key is actually used per route via cdmipIpRouteDesKey, so a compromised or expiring key can be replaced in one slot without reconfiguring every route that references a different slot. An admin rotating keys quarterly might load a fresh 48-hex-character key into slot 1 and repoint routes that were using key1 to the new value, while other routes on key2 continue using their existing, unaffected key.