10 September 2019

STANAG-4285, async Turkish "T-15"

05300.0 KHz/USB (intruding the 60mt amateur band), Turkish Mil prob. from Izmir area, TUR. STANAG-4285 600bps/L carryng async 5N1.5 (Turkish "T-15") stream: most likely encrypted pseudo-random naval broadcast since after removal of start/stop bits the resulting 5-bit stream does not autocorrelate (ACF = 0). A similar S4285 transmission but with 15/128 bits length period has already been reported here.
Notice that "T-15" is not an official name nor a well-known name: it's just a nickname I use in this blog to refer to this Turkish 15-bit format.


Signals and recordings gathered thanks to KiwiSDRs: kiwisdr.yo3iul.ro, sdr.ok2kyj.cz.


I gladly add a comment from my friend Valentin (cryptomaster): "The encrypted information was transmitted in "start-stop" mode with a 5-bit code with the addition of 1 bit - "start" and 1.5 bit stop. Since the transmitting equipment is designed to transmit an integer number of bits, the two halves of the code accumulated during the transmission are added up to one additional bit (0.5 + 0.5 = 1). Thus, a period of 15 bits is obtained.
The 5-bit code statistics are uniform, which confirms the use of encryption." 

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