11 December 2020

unid 216-bit Initialization Vectors


Interesting MIL 188-110A segments which transport encrypted data. The bitstreams corresponding to the eigth segments - after 110A removal - are shown in Fig. 2; unless segments e and f, each bitstream consists of an initial block followed by encrypted data.

Fig. 2 - demodulated bitstreams

The initial blocks consist of a 216-bit (27 bytes) sequence, most likely the initialization vector, which is 3 times repeated: obviously, the initialization vectors are different in each segment. It's to be notice thatsegment h (the last) is preceeded and followed by 3G-HF Fast Link Setup bursts (FLSU, BW5 waveform); most likely it's an incomplete recording of a 3G-HF Circuit Service mode using 110A.

Fig. 3 - 3x216-bit IV


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