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A2.3. Pseudo-Code Example

A2.3. Pseudo-Code Example​

The following pseudo-code illustrates the above algorithms for anti-replay and integrity checks. The values for 'Seql', 'Tl', 'Th' and 'W' are 32-bit unsigned integers. Arithmetic is mod 2^32.

     If (Tl >= W - 1)                            Case A
         If (Seql >= Tl - W + 1)
             Seqh = Th
             If (Seql <= Tl)
                 If (pass replay check)
                     If (pass integrity check)
                         Set bit corresponding to Seql
                         Pass the packet on
                     Else reject packet
                 Else reject packet
             Else
                 If (pass integrity check)
                     Tl = Seql (shift bits)
                     Set bit corresponding to Seql
                     Pass the packet on
                 Else reject packet
         Else
             Seqh = Th + 1
             If (pass integrity check)
                 Tl = Seql (shift bits)
                 Th = Th + 1
                 Set bit corresponding to Seql
                 Pass the packet on
             Else reject packet
     Else                                    Case B
         If (Seql >= Tl - W + 1)
             Seqh = Th - 1
             If (pass replay check)
                 If (pass integrity check)
                     Set the bit corresponding to Seql
                     Pass packet on
                 Else reject packet
             Else reject packet
         Else
             Seqh = Th
             If (Seql <= Tl)
                 If (pass replay check)
                     If (pass integrity check)
                         Set the bit corresponding to Seql
                         Pass packet on
                     Else reject packet
                 Else reject packet
             Else
                 If (pass integrity check)
                     Tl = Seql (shift bits)
                     Set the bit corresponding to Seql
                     Pass packet on
                 Else reject packet
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