RFC 1108 (rfc1108) - Page 3 of 17
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Alternative Format: Original Text Document
RFC 1108 U.S. DOD Security Option November 1991 2.3. Classification Level Field Length: One Octet This field specifies the (U.S.) classification level at which the datagram must be protected. The information in the datagram must be protected at this level. The field is encoded as shown in Table 1 and the order of values in this table defines the ordering for comparison purposes. The bit string values in this table were chosen to achieve a minimum Hamming distance of four (4) between any two valid values. This specific assignment of classification level names to values has been defined for compatibility with security devices which have already been developed and deployed. "Reserved" values in the table must be treated as invalid until such time they are assigned to named classification levels in a successor to this document. A datagram containing a value for this field which is either not in this table or which is listed as "reserved" is in error and must be processed according to the "out-of-range" procedures defined in section 2.8.1. A classification level value from the Basic Security Option in a datagram may be checked for equality against any of the (assigned) values in Table 1 by performing a simple bit string comparison. However, because of the sparseness of the classification level encodings, range checks involving a value from this field must not be performed based solely using arithmetic comparisons (as such comparisons would encompass invalid and or unassigned values within the range). The details of how ordered comparisons are performed for this field within a system is a local matter, subject to the requirements set forth in this paragraph. Table 1. Classification Level Encodings Value Name 00000001 - (Reserved 4) 00111101 - Top Secret 01011010 - Secret 10010110 - Confidential 01100110 - (Reserved 3) 11001100 - (Reserved 2) 10101011 - Unclassified 11110001 - (Reserved 1) Kent
