Checksum of the type 1

If the first parameter $A$ is equal to $1$ the checksum is generated in the manner described in this section.

The checksum stands before the block it belongs to.

The checksum property applies to the entire Fib object respectively Fib branch that is contained in the property element (its entire subobject), except those which have a separate / own checksum property. When loading the Fib object, blocks of the size of $C+B$ bits are loaded, where the block, wich lie at the end of the checksum field, is padded with $0$. From each Fib object it will be only read as much as belongs to the checksum field and the rest of the block is padded with $0$ .

If the checksum field $Cb_1$ is interrupted by another checksum field (object) $CB_2$, after the checksum field (object) $CB_2$ a new block for the checksum field $Cb_1$ will be start and read.

When storing the subobject of the property element of the checksum, the entire subobject is first brought into the compressed form, as described in this section 21 . From the created bit field, all areas which not belong to the checksum property are cut out, since they belong to different checksum properties, which are treated separately. As a result of this from the compressed subobject of the checksum property several bit fields $Bf_i$ for the checksum property are created. These bit fields $Bf_i$ are divided into blocks of $B$ bits, where each of the last blocks of a bit fields $Bf_i$ are padded with the 0 bit to $B$ bits. Then for each of the blocks the checksum of $C$ bits computed. After this step the blocks for each $Bf_i$ are assembled in their original order into bit fields, in which for each block first the checksum field of the block and then the associated data block comes. These bit fields are then concatenate into their original order with the other properties checksum fields, which were treated separately, into a bit field for the entire subobject.

The checksum is not only used for error detection, but if possible (if enough checksum bits are present) also for error correction.