Spoofing detection for underwater acoustic GNSS-like positioning systems

Transcription

1 Scentfc Journals of the Martme Unersty of Szczecn Zeszyty aukowe Akadem Morskej w Szczecne 019, 57 (19), ISS (Prnted) Receed: ISS (Onlne) Accepted: DOI: /34 Publshed: Spoofng detecton for underwater acoustc GSS-lke postonng systems Martme Unersty of Szczecn, Faculty of agaton 1 Wały Chrobrego St., Szczecn, Poland, e-mal: ochn@am.szczecn.pl Key words: antterrorsm, GSS, spoofer, antspoofng, spoofng detecton algorthm, underwater ehcle, underwater transport safety, acoustc communcaton Abstract The need for accuracy, precson, and data regstraton n underwater postonng and nagaton should be ewed as no less strngent than that whch exsts on the sea surface. In the same way n whch GSS (Global agaton Satellte System) receers rely on the sgnals from multple satelltes to calculate a precse poston, undersea ehcles dscern ther locaton by rangng to the acoustc sgnals orgnatng from seeral fxed underwater acoustc sources usng the Tme-of-Arral algorthm (ToA) through the Ordnary Least Squares method (OLS). In ths artcle, the scope has been lmted to only consderng underwater postonng systems n whch the nagaton receer s acoustcally passe. The receer lstens to the buoys, recees ther messages and soles the problem of fndng ts own poston based on the geographcal coordnates of the buoys. Often, such systems are called GSS-lke Underwater Postonng Systems (GSS-lke UPS). It s mportant to note the dstncton between general purpose GSS-lke UPS (manly cl systems) and specal purpose GSS-lke UPS (manly mltary systems). In ths artcle, only general purpose GSS-lke UPS systems hae been consdered. Dependng on the scale of system s serce areas, GSS-lke UPS are dded nto global, regonal, zonal and local systems. Only local GSS-lke UPS systems hae been consdered n ths artcle. The spoofng of acoustc GSS-lke UPS works as follows: the acoustc GSS sgnal generator transmts a smulated sgnal of seeral satelltes. If the leel of the smulated sgnal exceeds the sgnal strength of the real satelltes, the acoustc receer of an underwater object wll capture the fake sgnal and calculate a false poston based on t. All receers that fall nto the spoofng zone wll calculate the same coordnates, whle the receers located n dfferent places wll hae a msmatch n the XYZ coordnates. Introducton Marne surface and underwater floatng tools can sole many postonng problems: postonng of drllng shps, postonng whle loadng at sea, postonng the layng of cables and ppelnes, ensurng dng works, detecton of gas leaks, etc. There are many manufacturers of underwater postonng systems n the world (ROV, 018), ncludng HPAP Hgh Precson Acoustc Postonng (Kongsberg Martme, 016), Xblue (Xblue, 018), EoLogcs (EoLogcs, 018) Sonardyne (Sonardyne, 018) etc. It s necessary to hghlght the promsng desgn programs of three companes: DARPA (Defense Adanced Research Projects Agency), BAE Systems (Brtsh Aerospace) and the Charles Stark Draper Laboratory (Fgure 1) (BAE Systems, 016). DARPA has enlsted the serces of BAE Systems, along wth the not-for-proft research company Draper, to deelop a system that wll allow for GSS-lke precson underwater. The program s called the Postonng System for Deep Ocean agaton (POSYDO) and, f all goes to plan, t wll allow the nay s submersbles to reman concealed under the ocean whle accurately nagatng. 38 Scentfc Journals of the Martme Unersty of Szczecn 57 (19)

2 Spoofng detecton for underwater acoustc GSS-lke postonng systems Underwater acoustc source Unmanned Undersea Vehcle precsely postons tself by rangng to seeral underwater sgnals Fgure 1. DARPA, BAE Systems and Draper are deelopng undersea postonng technology that wll make use of long-range acoustc sources at fxed locatons n the ocean (Laars, 016) Ths system uses buoys that act as rong pseudoltes and translate the GSS serce to an acoustc-based serce under water. In the same way that GSS receers rely on the sgnals from multple satelltes to calculate a precse poston, the undersea ehcles dscern ther locaton by rangng to the acoustc sgnals from seeral of the fxed underwater acoustc sources. In ths artcle, the scope has been lmted to consderng only those underwater postonng systems n whch the nagaton receer s acoustcally passe. The receer lstens to the buoys, recees ther messages and soles the problem of fndng ts own poston based on the geographcal coordnates of the buoys. Often, such systems are called GSSlke underwater postonng systems (GSS-lke UPS). It s mportant to note the dstncton between general purpose GSS-lke UPS and specal purpose GSS-lke UPS. In ths artcle, only general purpose GSS-lke UPS has been consdered. Dependng on the scale of the system s serce areas, GSS-lke UPS s dded nto global, regonal, zonal and local systems. In ths artcle, only local GSS-lke UPS systems hae been consdered. The four man methods used n determnng underwater postonng, whch largely concde wth the methods of measurng the coordnates of moble objects n rado networks, should be noted: 1. Receed Sgnal Strength (RSS) the dstance to the object s estmated from the power of the sgnal. Ths method works well oer short dstances.. Angle of Arral (AoA) the locaton of the object s determned wthn the area of a trangle formed by the ntersecton of the axes of the antenna patterns of the sectors of three base statons (modfed trangulaton method). 3. Round TrpTme (RTT) the object sends a sgnal to the transceer and wats for a response. The half-dfference between the tme of sendng a sgnal to an object and receng a sgnal from an object multpled by the speed of lght ges the dstance to the object. 4. Tme of Arral (ToA) a technque n whch the tme of arral of a specfc sgnal, whch s precsely synchronzed wth the tme of orgn, s calculated (ths method requres tme synchronzaton between the sender and recpent). The creaton optons of underwater acoustc GSS-lke postonng systems A. Wre GSS-lke UPS The frst type s wred or buoyant underwater GSS. A GSS receer mounted on a buoy s towed on the surface by underwater targets such as underwater ehcles (Fgure ). A cable or fber s used to send the GSS poston to the underwater target. Ths technque does not ge the true poston of the target but the false poston een wthn a few tens of meters around the surface buoy, so that t s called a wred underwater GSS (Kaushal & Kaddoum, 016). Postonng accuracy s determned by cable length; therefore, ths type of postonng s sometmes called false GSS-lke UPS (Scuba Dng Chcago, 013). Fgure. Wre GSS-lke UPS; S 1, S and S 3 satelltes of GSS; B floatng GSS antenna of an underwater ehcle B. Drect GSS-lke UPS The second type s a drect underwater GSS soluton (Fgure 3). In 199, Youngberg nspred the drect transposton of a GSS sgnal to the underwater world (Thomas, 1998). Acoustc waes but not rado electrcal sgnals drectly go from the surface buoys that are replacng the satelltes to the underwater moble unts (receers). Then, the underwater platform recees these acoustc messages from the buoys equpped wth GSS receptors and computes ts own poston. M. Youngberg of the US-AIR FORCE patented and publshed ths soluton (Youngberg 1991). Zeszyty aukowe Akadem Morskej w Szczecne 57 (19) 39

3 calculated and dsplayed usng an algorthm (Hubert, 1966). In ths artcle, the scope has been lmted to drect underwater acoustc GSS-lke postonng systems. From TCP/IP spoofng to underwater spoofng Fgure 3. Drect GSS-lke UPS: S 1, S and S 3 satelltes of GSS; B 1, B and B 3 sonar transponders of the GSS sgnals The surface buoys determne the XY coordnates (Z = 0) and tme T, based on whch the receer of the GSS-lke sgnals then determnes ts own XYZ coordnates. In some applcatons for an underwater essel, only the XY coordnates are sgnfcant, snce the depth Z of the de can be determned by a depth gauge, so the calculatons of the XY coordnates hae been solely focussed on n ths paper. C. Reerse GSS-lke UPS The thrd type s ery smlar to the second type of soluton, but t s a reerse underwater GSS soluton. Ths method has been recently nestgated by Hubert Thomas (Hubert, 1966) and s aalable commercally: the so-called GSS Intellgent Buoy (GIB) system, deeloped by ACSA n Ths system s desgned to track the poston of an underwater target, equpped wth an acoustc emtter, by measurng the tmes of arral of the acoustc sgnals at a set of surface buoys equpped wth submerged hydrophones and GSS receers. Each buoy has a GSS receer, a clock synchronzed wth a GSS clock, a sonar receng system wth a recessed transducer, and a rado modem (GIB technology Global Intellgent Buoy). Each buoy measures ts own coordnates and lag tmes at predetermned tmes and transmts them along wth the coordnates n the MEA standard a rado modem to the essel. Accordng to the data of the receed delay tmes of the pnger sgnals, and takng nto account the speed of sound n water, the dstances from the underwater object to each of the buoys can be calculated on board the essel. The coordnates of the underwater object and all the buoys are then The easest way to nterfere wth a GSS receer s to just generate rado nterference or create a false nose sgnal (Jammng), whch s stronger than the real sgnal. Howeer, n ths case, the GSS receer wll smply stop workng and the ctm wll swtch to IS postonng. In the more ntellgent Spoofng technque, the ctm does not know that the sgnal receed by the GSS receer s ncorrect. The spoofer creates a false sgnal and thus the ctm determnes the wrong tme and locaton. Intally, the term spoofng was used as a term for network securty, mplyng the successful falsfcaton of certan data n order to gan unauthorzed access to a partcular network resource (Spoofng TCP/IP & UDP). Oer tme, ths term began to be used n other areas of nformaton securty: Caller ID spoofng substtuton of the callng phone number n VoIP-networks. E-mal address spoofng substtuton of the emal address of the sender. Extenson Spoofng fle extenson spoofng. Fle ame Spoofng clonng the fle name. Source Code Spoofng substtuton of page content and the source code. GSS Spoofng substtuton of nagaton data from satelltes n order to decee the ctm. Intally, the spoofer sends the correct coordnates, but gradually rejects the sgnal to the sde. Dong ths slowly s necessary so that the GSS receer does not block all sgnals due to an abrupt change n locaton. Underwater Spoofng formally, t s not much dfferent from telecommuncatons spoofng. The prncpal dfference s the use of acoustc sgnals, often for mltary applcatons (Mortmer, 016). Underwater GSS Spoofng substtuton of nagaton data from surface rado-acoustc or underwater acoustc buoys n order to decee the ctm. The spoofer can be a surface or underwater manned or unmanned ehcle. Underwater acoustc GSS-lke postonng systems reman the predomnant nagaton soluton for both commercal and mltary underwater applcatons. Howeer, proen threats to GSS-lke UPS 40 Scentfc Journals of the Martme Unersty of Szczecn 57 (19)

4 Spoofng detecton for underwater acoustc GSS-lke postonng systems from jammng, spoofng, and enronmental blockages hae connced the mltary that, as well as many commercal technology frms, now s the tme to fnd new nagaton solutons that can enhance the securty of GSS-lke UPS. The man strategy of spoofng s as follows. A deeloped spoofer smulates the GSS-lke UPS sgnals n such a way that at the moment of the ctm s capture, the false coordnates concde wth the real ones and then smulate the moement of the ctm along a certan trajectory (Fgure 4). { x ~, ~ y, ~ z } ctm s XYZ coordnates, as measured by the spoofer. {Δx, Δy, Δz } amendment of the ctm s coordnates to take the ctm away from a gen route. arral T = (t t sent ) the measured sgnal s propagaton tme from the buoy B to the spoofer usng the buoy s sgnals, or to the ctm wth the help of a false sgnal from the spoofer. c the speed of lght. The underwater acoustc GSS-lke postonng of a spoofer and ts ctm Solng the system of equatons (1) allows for the ctm s coordnates to be calculated:, y, z y z z ct, 1, (1) Fgure 4. The man strategy of spoofng: S 1, S and S 3 satelltes of GSS; B 1, B and B 3 sonar transponders of GSS sgnals There are two strateges for underwater spoofng: spoofng based on receng GSS sgnals from nagaton satelltes, spoofng based on receng acoustc sgnals from nagaton buoys. In ths artcle, the scope has been lmted to receng acoustc sgnals from nagaton buoys. otatons and defntons z 0 (x, y) the known depth of the sea at the pont (x, y). B {x, y, z }, 1, buoys of GSS-lke UPS, the number of buoys. Acoustc Spoofng an attack on a GSS-lke UPS, n an attempt to decee the ctm s receer by transmttng powerful false sgnals that mmc the sgnals from the true GSS-lke UPS, exceedng the power of the true sgnal. Acoustc Spoofer specal purpose computer, rado and acoustc equpment for the mplementaton of acoustc spoofng. {x s, y s } spoofer s XY coordnates (z s = 0, because n ths artcle, the scope has been lmted to surface spoofers only). {x, y, z } ctm s XYZ coordnates, as measured by the ctm. where T measured propagaton tme of a real sgnal from the buoy B to the ctm. The system of equatons (1) can be wrtten as: 1 y z z ε x, y, z ct () In the general case, the soluton () s carred out usng the numercal mnmzaton methods (3):, y, z arg mn ε, y, z (3) x, y, z There s enough data from three buoys to determne {x, y, z }, howeer, as the software smulaton of GSS-lke UPS shows, due to the approxmate nature of the measurement of pseudoranges (ρ ct, 1, ), the postonng accuracy {x, y, z } wll depend on the number of buoys. If the ctm uses a barometrc depth gauge to determne z, the system of equatons (1) takes the form: x y y ct, 1 (4), In ths case, the soluton (4) can be carred out as: arg mn x, y 1, y y ct (5) Solng the system of equatons (6) allows the spoofer s coordnates {x s, y s } to be calculated: Zeszyty aukowe Akadem Morskej w Szczecne 57 (19) 41

5 arg mn x, ys s 1 x, y y ct s s s s (6) When determnng the coordnates {x s, y s }, there wll be enough data from three buoys or three GSS satelltes f the spoofer s on the surface of the sea. Supposng that the ctm s coordnates {x, y, z } are known; for example, by usng a sonar range fnder and a measured drecton to the ctm. If the ctm does not use a barometrc depth gauge for determnng z, then n ths case t s possble to determne the correctons ΔT for the measured tme T so that the ctm s receer would calculate the fake coordnates that are equal to the true ones (7): 1 arg mn y y z z ct T x, y, z x, y, z (7) If the power of the spoofer s sgnal exceeds the power of the buoys sgnals, the ctm s receer wll swtch to receng the false sgnal. Furthermore, the spoofer then apples an escapng spoofng strategy n accordance wth the equaton: y y y z z ct T, 1, (8) where {Δx, Δy, Δz } the amendment of the ctm s coordnates; takng the ctm away from ther route. In ths stuaton, the spoofer s n an acte state on the sea surface and the alue z = 0,.e. correspondng to a zero sea leel. The algorthm for fndng ΔT, 1, wth gen ectors {x, y, z } and {Δx, Δy, Δz } has not been consdered n ths artcle. In the concluson of ths secton, the workng method of D GSS-lke UPS (Fgures 5 and 6) and a D GSS-lke Underwater Spoofng has been shown usng an example of a sonar sgnal repeater (Fgures 7 and 8). Consder an extremely smplfed case when underwater postonng s mplemented n only one plane (D GSS-lke UPS, Fgures 5 and 6). The clock on the buoys and the underwater ehcle are synchronzed. The approprate processng of the data from the nagaton satelltes ensures the hgh accuracy of the clock on the buoys. Fgure 5. D GSS-lke UPS: B 1, B and B 3 sonar transponders of GSS sgnals; D 1, D and D 3 real dstances from the ehcle to the transponders; D 1 + ΔD, D + ΔD and D 3 + ΔD measured dstances from the ehcle to the transponders; ΔD the dstance measurement error due to the msmatch between the transponder s clock and the ehcle s clock The transt tme of the nagaton sgnal from the satellte to the hydrophone depends not only on the dstance, but also on the state of the onosphere, the atmosphere and water, therefore an accurate measurement of the dstance from the satellte to the hydrophone s mpossble. The sgnfcant error ΔD n the measurement s caused by the naccuracy of the ehcle s on-board clock, creatng a zone of uncertanty, shown n Fgure 5 as a red fgure, close to a trangle. Based on an terate process of successe approxmatons, ths zone can be compressed and moed to a pont as close as possble to the exact coordnates of the ehcle (Fgure 6). Fgure 6. The fnal stage of the procedure of successe approxmatons of D GSS-lke UPS: B 1, B and B 3 sonar transponders of GSS sgnals; D 1, D and D 3 real dstances from the ehcle to the transponders The spoofer-translator (Fgure 7) recees acoustc sgnals from the transponders and transmts them wth more power, whch s suffcent to shft the ehcle s attenton from the real sgnals to the false ones. The dstance ΔD' from the spoofer-translator to the ehcle s added to the results of the measured dstances (pseudo-dstances). 4 Scentfc Journals of the Martme Unersty of Szczecn 57 (19)

6 Spoofng detecton for underwater acoustc GSS-lke postonng systems Fgure 7. D GSS-lke Underwater Spoofng: B 1, B and B 3 sonar transponders of GSS sgnals; D 1, D and D 3 real dstances from the spoofer to the transponders; D 1 + ΔD, D + ΔD and D 3 + ΔD measured dstances from the ehcle to the transponders; c ε t the dstance measurement error due to the msmatch between the transponder s clock and the ehcle s clock; ΔD the dstance between the spoofer and the ehcle Based on an terate process of successe approxmatons, ths zone ΔD = c ε t + ΔD' wll then be compressed and moed to a pont as close as possble to the exact coordnates of the spoofer-translator (Fgure 8). Fgure 8. The fnal stage of the procedure of successe approxmatons for D GSS-lke Underwater Spoofng: B 1, B and B 3 sonar transponders of GSS sgnals; D 1, D and D 3 real dstances from the spoofer to the transponders; the ehcle determnes ts coordnates, whch concde wth the coordnates of the spoofer-translator; ΔD' the dstance between the spoofer-translator and the ehcle Spoofng detecton usng a sngle hydrophone In two next sectons, the results obtaned n the lterature (Caparrn et al., 007, Humphreys at al., 008, Jafarna-Jahrom at al., 01) and the author s own research results (Dobryakoa, Lemeszewsk & Ochn, 01; 013; 014; Dobryakoa et al., 013) hae been ntroduced and the two methods of spoofng detecton hae been dscussed: 1) the method of measurng the coordnates of a mong ctm at two ponts on the route usng a sngle hydrophone (n ths case usng a conentonal hydrophone, that s, the problem of the practcal mplementaton of the spoofng detecton of GSS-lke UPS s reduced to programmng only); ) the method of measurng the coordnates of a ctm at two ponts n space usng a dual hydrophone. A fxed sngle hydrophone can be nstalled on the spoofng detector. ote that the ctm may be n moton. A. The measurement of the spacng between two postons of the sngle hydrophone n nagaton mode The spoofng detector measures the coordnates of the hydrophone H, based on the real sgnal from the buoys: 1 arg y z z mn x, y, z ct (9) where (x ', y ', z ' ) the unknown precse coordnates of the hydrophone H at the tme t'; ( y z) the calculated coordnates of the hydrophone H at the tme t'. The spoofng detector agan measures the XYZ coordnates of the hydrophone H at the tme t": 1 arg y z z mn x, y, z ct (10) where (x ", y ", z " ) the unknown precse coordnates of the hydrophone H at the tme t"; ( y z ) the calculated coordnates of the hydrophone H at the tme t". The measured dstance between the hydrophone at the tmes t' and t": Dˆ ˆ yˆ yˆ zˆ z (11) ˆ 1 ths must be commensurate wth the dstance traelled by the ehcle oer tme (t" t),.e.: D ˆ V t t (1) 1 Zeszyty aukowe Akadem Morskej w Szczecne 57 (19) 43

7 B. The measurement of the spacng between two postons of a sngle hydrophone n spoofng mode The spoofng detector measures the coordnates of the hydrophones, based on the false sgnal from the spoofer: arg mn x, y, z x x y y z z ct 1 (13) where (x ', y ', z ' ) the unknown precse coordnates of the hydrophone H at the tme t'; ( y z) the calculated coordnates of the hydrophone H at the tme t'. The spoofng detector agan measures the XYZ coordnates of the hydrophone H at the tme t": arg mn x, y, z x x y y z z ct 1 (14) where (x ", y ", z " ) the unknown precse coordnates of the hydrophone H at the tme t"; ( y z ) the calculated coordnates of the hydrophone H at the tme t". The measured dstance between the hydrophone H at the tme t' and the hydrophone Y at the tme t" can be wrtten as: ˆ yˆ yˆ zˆ zˆ 0 ˆ 1 D (15) snce all the hydrophones n the spoofng zone wll calculate the same false coordnates and Dˆ 1 must be ncommensurable wth the dstance traelled by the ehcle oer tme (t" t'),.e.: C. The decse rule D ˆ V t t (16) 1 Comparng equatons (1) and (16), the decse rule for detectng spoofng can be wrtten as: ˆ f D 1 Ď then go to Spoofng (17) where Ď dscrmnant, whch can be determned on the bass of statstcal studes at the desgn stage of a real detecton system. At present, theoretcal studes and releant real sea tests are beng carred out at arous speeds V and arous alues Δt = (t" t') n order to fnd acceptable alues of Ď. It should be noted that the spoofng detector may be n moton. Durng the tme Δt = (t" t'), the parameters of the spoofer s sgnals may change, therefore solng the problem of optmzng the parameters of the spoofng detector, and t s necessary to mnmze the parameter Δt. From the pont of ew of detectng spoofng, t s necessary to maxmze the parameter Δt. In order to resole ths contradcton, the mnmax methods of parametrc optmzaton can be used (Ehrgott, Ide & Schöbel, 014). Mnmax s a type of backtrackng algorthm that s used n decson makng and game theory n order to fnd the optmal moe for a player, assumng that the player s opponent also plays optmally. It s wdely used n two player turn-based games such as Tc-Tac-Toe, Backgammon, Mancala, Chess, etc. Spoofng detecton usng dual hydrophones Two fxed hydrophones H' and H" can be nstalled on the spoofng detector at a dstance D from each other. ote that the spoofng detector may be statonary or n moton. D. The measurement of the dstance between the hydrophones n nagaton mode The spoofng detector measures the coordnates of the hydrophone H': arg mn x, y, z x x y y z z ct 1 (18) where (x ', y ', z ' ) the unknown precse coordnates of the hydrophone H'; ( y z) the calculated coordnates of the hydrophone H'. The spoofng detector then measures the coordnates of the hydrophone H": arg mn x, y, z x x y y z z ct 1 (19) where (x ", y ", z " ) the unknown precse coordnates of the hydrophone H" at the tme t'; ( y z ) the calculated coordnates of the hydrophone H". 44 Scentfc Journals of the Martme Unersty of Szczecn 57 (19)

8 Spoofng detecton for underwater acoustc GSS-lke postonng systems The measured dstance between H' and H" can be calculated from: ˆ yˆ yˆ zˆ z D Dˆ ˆ 1 (0) where D the real dstance between the hydrophones. E. The measurement of the dstance between the hydrophones n spoofng mode Due to the fact that all the hydrophones n the spoofng zone calculate the same false coordnates, the equaton (0) takes the form: ˆ yˆ yˆ zˆ zˆ 0 ˆ 1 D F. The decse rule (1) Comparng equatons (0) and (1), the decse rule for detectng spoofng can be wrtten as: ˆ f D 1 Ď then go to Spoofng () where Ď the dscrmnant, determned on the bass of statstcal studes at the desgn stage of a real detecton system. Conclusons Ths paper has dscussed the spoofng detecton of underwater acoustc GSS-lke postonng systems through the use of sngle and dual hydrophones and the key to solng the challenge of prodng relable postonng. The accessores that are necessary for the manufacture of systems for underwater acoustc jammng and/or spoofng are now wdely aalable Table 1. The man characterstcs of spoofng detecton methods Type of spoofng detecton Type of ctm umber of spoof hydrophones umber of ctm s hydrophones eed for ctm s moement Usng a sngle hydrophone Underwater essel Usng dual hydrophones Underwater essel Yes o and ths type of attack can be utlzed by the mltary, but also by terrorsts. The dstorton of the sgnal ncludes sgnal capture and playback at the same frequency wth a slght shft n tme and wth greater ntensty, n order to decee the acoustc equpment of an underwater essel. The man characterstcs of spoofng detecton methods hae been shown n Table 1. The rato of the allowable eloctes of the spoofer and the ctm, for the method usng a sngle hydrophone, requres addtonal nestgaton. References 1. BAE Systems (016) Undersea nagaton and postonng system deelopment to begn for U.S. ay. [Onlne] May 16. Aalable from: /undersea-nagaton-and-postonng-system-deelopment -to-begn-for-u-s nay [Accessed: January 0, 018].. Caparrn, M., Egdo, A., Soulat, F., German, O., Farres, E., Dunne, S. & Ruffn, G. (007) Oceanpal : montorng sea state wth a GSS-R coastal nstrument. Paper presented at the Internatonal Geoscence and Remote Sensng Symposum. IEEE, Barcelona, Span, 3 8 July 007, do: /igarss Dobryakoa, L., Lemeszewsk, Ł. & Ochn, E. (01) Antterrorsm desgn and analyss of GSS antspoofng algorthms. Scentfc Journals of the Martme Unersty of Szczecn, Zeszyty aukowe Akadem Morskej w Szczecne 30(10), pp Dobryakoa, L., Lemeszewsk, Ł. & Ochn, E. (013) The analyss of the detectng algorthms of GSS-spoofng. Scentfc Journals of the Martme Unersty of Szczecn, Zeszyty aukowe Akadem Morskej w Szczecne 36(108) z., pp Dobryakoa, L., Lemeszewsk, Ł. & Ochn, E. (014) Desgn and Analyss of Spoofng Detecton Algorthms for GSS Sgnals. Scentfc Journals of the Martme Unersty of Szczecn, Zeszyty aukowe Akadem Morskej w Szczecne 40 (11), pp Dobryakoa, L., Lemeszewsk, Ł., Lusznko, E. & Ochn, E. (013) The study of the spoofer s some propertes wth help of GSS sgnal repeater. Scentfc Journals of the Martme Unersty of Szczecn, Zeszyty aukowe Akadem Morskej w Szczecne 36 (108) z., pp Ehrgott, M., Ide, J. & Schöbel, A. (014) Mnmax robustness for mult-objecte optmzaton. European Journal of Operatonal Research 39, 1, pp EoLogcs (018) Underwater Acoustc LBL Postonng Systems. [Onlne]. Aalable from: /en/products/lbl/ndex.html [Accessed: January 0, 018]. 9. Hubert, T. (1966) Method and dece for the montorng and remote control of unmanned, moble underwater ehcles. Unted States Patent 5, US pdf 10. Humphreys, T.E., Ledna, B. M., Psak, M.L., O Hanlon, B.W. & Kntner, P.M. Jr. (008) Assessng the Spoofng Threat: Deelopment of a Portable GSS Clan Spoofer. Preprnt of the 008 IOGSS Conference Saanna, GA, September Zeszyty aukowe Akadem Morskej w Szczecne 57 (19) 45

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