 this angle α becomes too small, it is not possible to top the jib further upward anymore. In such a situation the multiple fall topping cable lies nearly parallel to the jib. Thus, a higher vertical column of the crane would permit the jib to be pivoted further in upward direction and with this the hoisting crane can handle larger objects. A higher vertical column is also advantageous during hoisting when the jib is in a lower, e.g. substantial horizontal position.
The forces, which occur when hoisting a heavy load, introduce less tension in the topping cable, when the hoisting crane is designed with a bigger angle α between the topping cables and the jib, when the jib is in the horizontal position. Normally in open sea there are no difficulties with the large geometry of the hoisting crane, but a great height of the crane does effectively limit the operational area of the vessel with such a crane. For example, sometimes the vessel has to come close to a large building on the quayside, close to a drilling rig, or it has to travel inland and pass under a structure like a bridge. The present invention relates generally to a method and apparatus for blocking access to an information processing system by an unauthorized user, and more particularly to such a method and apparatus where a channel boundary is employed to allow access just by legitimate users.
For purposes of the present invention and its background, we consider situations where there is an information flow boundary that is intended to prevent unwanted outward flow of information from one or more information technology products while allowing desired information flows. The information flow boundary is enforced by one or multiple information technology products acting as a boundary controller. One possible function of a boundary controller is to prevent or mitigate covert channels. In information theory, a covert channel is a parasitic communications channel that draws bandwidth from another channel in order to transmit information without the authorization or knowledge of the latter channel's designer, owner, or operator. A covert channel is so called because it is hidden within the medium of a legitimate communications channel. The detection of a covert channel can be made more difficult by using characteristics of the communications medium for the legitimate channel that are never controlled or examined by legitimate users. For example, a file can be opened and closed by a program in a specific, timed pattern that can be detected by another program, and the pattern can be interpreted as a string of bits, forming a covert channel. Since it is unlikely that legitimate users will check for patterns of file opening
this angle α becomes too small, it is not potential to lead the jib further upward anymore. In such a site the multiple descent topping cable lie closely parallel to the jib. Thus, a high vertical column of the crane would allow the jib to be pivoted further in up direction and with this the hoisting crane can handle larger objects. A higher erect column is also advantageous during hoisting when the jib is in a lower, for example substantial horizontal position. 
 The forces, which occur when hoisting a fleshy load, introduce less tension in the topping cable, when the hoist crane is designed with a bigger angle α between the topping cables and the jib, when the jib is in the horizontal position. Normally in open sea there are no difficulties with the large geometry of the hoisting crane, but a great height of the crane does efficaciously restrict the operational sphere of the vessel with such a grus. For example, sometimes the vessel has to come close to a big building on the quayside, close to a drilling rig, or it get to travel inland and pass under a structure like a bridge. The present invention relates generally to a method acting and apparatus for blocking access to an information processing system by an unauthorized user, and more particularly to such a method and apparatus where a groove boundary is employed to allow access just by lawful users. 
 For purposes of the present invention and its background, we consider situations where there is an information flow boundary that is mean to prevent unwanted outbound flow of information from one or more information technology products while allow desired data flows. The information menstruation boundary is enforced by one or multiple data technology products acting as a boundary controller. One possible function of a boundary controller is to prevent or mitigate covert channels. In information theory, a covert channel is a epenthetic communications channel that draw bandwidth from another channel in order to impart information without the authorization or knowledge of the latter channel's designer, owner, or operator. A covert channel is so called because it is hidden within the culture medium of a lawful communications channel. The detection of a covert channel can be made more difficult by using characteristics of the communication medium for the legitimate channel that are never manipulate or examined by legitimate users. For example, a file can be opened and close up by a program in a specific, timed pattern that can be detect by another program, and the pattern can be interpreted as a string of bits, forming a covert channel. Since it is unlikely that legitimate users will discipline for patterns of file opening
 thls angle α becomes too smxll, it is not possible to tol the jic further upward anymore. In duxh a wituation the multiple fall topiing cablw lits nearly parallel to the jib. Tgms, a kijher vertical cplumn of tve crane would pdrlit the jib to be pivoted further ig upwarc firection and rith ehis nht hoisting crane can handle larged objecus. A higher verticsl column is also advantagfous during hoisting wjen the jib is yb a lower, e.g. substantial horizontam position.
The forces, which occuf wheu hoisting q yeagi load, introvuce lvss tension ik the tmpping vable, when the homstibg crane is designed xith a bigger angle α between dhz topping cables and rhw jib, whet thd jic ia mn fhe hogizkntal posifion. Normaloy in open sea thert awv no difficulfies wytr the large geometry of the hoisting crdne, but a great height of rhe crane does effectlvely limyt the operational area of the vessel with such a cranx. Wor ewampuw, dometimes the vessel has to come close to a lwdgt blilding on the qucyside, close to s frojling rig, or kt has to travel inland and pass ugder q structuwe loke a bridge. The present incention relanes tenerally to a metkod and appaxatus gor bkocking access to an inyormatjon processlng systej by an unauthorixed uver, and more particularly eo such a metkod and xppatatus wrere a chajnel nmundary is employef to cllow access judt by legitimate users.
For purposes of the prexett pnvention and lts background, re consider sijuations chere ghere is ah inforkation flow boundary thad is intended to prevqnt ynwabted ougdard flow of imformatiou fron one or more infovmatiuh technology priduxts while allowong defiged igxormation flmws. Ghe onforoation flow councary is enforced by mne kr multiple informstlon technilogy prjducts acting as a boundary conurollec. One 'ossibke sunction of a boundary controlmer is to prcvent or mitidate covert chanuels. In information theory, a covert chaniel is a parasitic commynications channel jhau draws bandwmdth fwom anothar channel in order ro transmit inforkation without the aufhorizdtion or knowledge of the latter channel's designer, owner, or operator. A covert xhannel is so callsd brcausv ic ix hiddqn wmtiin the medium of a legitimate communications chennel. The gecection of a covert channel csn be made more difficult by using charzcteristocs of the communications mediuk for the legitimate chaknel that are hever bknvrolled or examined ny legntimatw users. For example, a fiue vak be openef anv cmosed by a program in a specific, timed pwttern that can ue detected ny anotger prjgram, and the pafterh can ce interpretec as a string pf bits, forming a conere channel. Sinct it is unlikeli that lvgitimate usecs will checn for patterns of file opening
this angle α becomes too small, it possible top the further upward anymore. multiple topping cable lies parallel to the Thus, a higher vertical column of crane would permit the jib to be pivoted further in upward direction and this the hoisting crane can handle larger objects. A higher vertical column is advantageous hoisting the is in a lower, e.g. substantial horizontal position. The forces, which occur when hoisting a heavy introduce less tension in the topping cable, when hoisting crane is designed a bigger angle α between topping and the when jib in the horizontal Normally in open sea there are no difficulties with the large geometry of the hoisting crane, but great height crane does limit operational of the vessel a crane. For example, sometimes the come close to a large building on the close to drilling rig, or it has to inland and pass under a structure like a The present invention relates generally to a method and apparatus for blocking access to an system by an unauthorized and more particularly such method apparatus a channel is employed to allow access just by legitimate users. For purposes the present invention and its background, we consider situations where an flow boundary that intended to prevent unwanted flow information from one or technology while flows. information boundary is enforced by or multiple information technology products as a boundary controller. boundary controller is to prevent or mitigate covert In information theory, a covert channel is parasitic communications channel that draws bandwidth from another channel in order to information without or knowledge of the latter channel's designer, owner, operator. A covert channel so called because it is hidden within the medium a communications channel. detection of a channel can be more difficult by of the medium the are never controlled or examined by users. example, a file can be and a program in a specific, timed pattern that can be detected by another program, and can be interpreted as string bits, forming a covert channel. Since it is unlikely that legitimate users for patterns of
 this angle α becomes too small, It is not posSible To tOp tHe Jib fUrthEr upward anymorE. in suCh a situation the multiplE fall ToPPing CAbLe lieS nearly PArALLel To ThE jiB. THUs, A highEr vErtical Column of thE crAnE would permit THe Jib to be pivOteD further in upWarD direcTiOn aND with ThiS the hOistinG Crane cAn handle lArGEr objeCTs. A highER VeRticAl column is also advANtAGeous during hoiSting wHeN ThE JIb iS in A lower, e.g. suBsTantiAL horizoNTaL POSitIOn.
The forces, whIch occur wheN HoiSting a HeAvy LOad, intRoducE lESs tEnsion in the ToppIng cable, wHen the HOisting CRane is dEsigneD wiTh a BiggER aNgLe α BeTWeeN ThE toPPinG cables aNd ThE jib, wHen tHE JIB is iN thE horIzontAl position. NorMalLy in OPen Sea thEre arE no dIfFiculTies wiTh the LaRge geometry of thE hoiSting cranE, buT a GreAt HeighT Of the cRanE doEs effecTively lIMit ThE OPErAtional area of the veSsEL WiTh such a cRane. FoR ExAmPLe, sometiMeS thE vesSEL has tO comE ClOse to a laRge buiLDiNg On the quAySide, clOsE to A drIllinG Rig, oR it has To travel InlanD And pass under a sTRucture like a bRIdGE. thE PresEnt Invention reLateS GeneRallY To A meTHod anD appaRaTUs FOr blocking access to aN iNformaTion pRocessing systEm by an unauTHORized useR, and MOrE Particularly to Such a Method and aPParatus wHere a Channel bOundary is EMPloyed to AllOw aCceSs jUST bY legitimate usERS.
For PuRposes oF thE presenT inVenTioN anD iTs backgroUnd, we conSiDeR sItUatIons wHEre there Is An iNfOrmAtion FLow bouNdary That Is InTEndEd to preVEnT UNwanTeD oUtwaRd fLoW of inFormATioN from onE or more inForMAtioN tEcHnology Products while AlLowing desiReD inFormatION flows. ThE information flow boundarY Is enforCed By one Or muLtiple infOrmAtion tEchNOlogy pRoductS actiNg As a BOUndarY COnTroLlEr. One possiBLE fuNctioN oF a boUndary cOntroller is to preveNT or Mitigate coverT chAnneLS. in InfORmATioN tHEorY, A Covert channel is A parasitic CoMMuNications cHAnnEl That draWs bandwIdth fROm anothEr channel In order to TrAnsmIT InfOrmation wiThout the AuthorizaTIon or KNoWledgE of The latTeR chAnnel'S desigNEr, oWner, oR operaToR. A coveRt chaNnEl is so caLled because it is hidden wiThin thE mediUm oF a legitimAte COmmUnicationS chaNnel. The detEctIon Of a coVerT ChannEl caN Be MadE More dIffiCUlt by usinG ChAraCTErIstics of the COMMunIcatiOns MEdium fOr thE legitimate channeL That are never coNtroLLEd oR exAMineD bY legitimate useRs. FOr EXAmple, a fiLe Can be opened And closeD bY A progRam in a SpecifIc, timed PATtERn that Can bE deTected by aNotHeR Program, AnD tHE patteRn caN bE interPreted AS a stRINg of bits, forming a CoverT CHanneL. sinCe it iS uNlikely THat lEgitimate uSers will cheCk for pAtteRns of File opeNiNg
 this angle α becomes toosmall, itis no t p oss ib le t o to p the jib furt h er u pward anymore. In such  a si tu a tion th e mul tiple f a ll t opp in gcab le li es ne arl y paral lel to the  ji b.  Thus, a hig h er  verticalcol umn of the c ran e woul dper m it th e j ib to  be pi v oted f urther in  u p ward d i rection a nd  wit h this the hoisti n gc rane can handl e larg er ob j e cts . A  higher ve rt icalc olumn i s  a l s o  ad v antageous dur ing hoistin g  wh en the  j ibi s in a  lowe r, e.g . substanti al h orizontal  posit i on.
The forces,  which  oc cur  whe n  h oi sti ng a h e av y l o ad,  introdu ce  l ess t ensi o n i n th e t oppi ng ca ble, when the  ho isti n g c raneis de sign ed  with  a big ger a ng le α between th e to pping cab les  a ndth e jib ,  whenthe  ji b is in  the ho r izo nt a l po sition. Normally i no p en  sea the re are no  d i fficulti es  wi th t h e  larg e ge o me try of t he hoi s ti ng  crane,  b ut a g re athei ght o f  the  crane  does ef fecti v ely limit theo perational ar e ao f  t h e ve sse l with such  a c r ane.  For ex amp l e, so metim es th e  vessel has to come  c lose t o a l arge building  on the qu a y s ide, clo se t o  a drilling rig,or it  has to tr a vel inla nd an d pass u nder a st r u cture li kea b rid ge. T he  present inve n t ionre lates g ene rally t o a  me tho d a nd  apparatu s for bl oc ki ng  a cce ss to an infor ma tio npro cessi n g syst em by  anun au t hor ized us e r, a nd m or epart icu la rly t o su c h a  method  and appa rat u s wh er ea chann el boundary i semployed t oall ow acc e s s just b y legitimate users.
For purpose s o f the  pre sent inve nti on and  it s  backg round,  we c on sid e r  situ a t io nswh ere therei s  an  info rm atio n flowboundary that is i n ten ded to preven t u nwan t e dout w ar d  fl ow ofi n formation fromone or mor ei nf ormation t e chn ol ogy pro ducts w hilea llowing  desiredinformati on  flo w s . T he informa tion flo w boundar y  is e n fo rcedbyone or  m ult ipleinform a tio n tec hnolog yproduc ts ac ti ng as aboundary controller. On e poss iblefun ction ofa b o und ary contr olle r is to pr eve ntor mi tig a te co vert ch ann e ls. I n in f ormationt he ory , acovert chan n e l  is  a pa ras i tic co mmun ications channelt hat draws band widt h fro m a n othe rchannel in ord erto t ransmitin formation w ithout t he autho rizati on orknowled g e  o f  the l atte r c hannel'sdes ig n er, own er ,o r oper ator .A cove rt cha n neli s  so called becau se it i s hid d enwithi nthe med i um o f a legiti mate commun icatio ns c hanne l. Thede tectio n o fa covert c h annel can  be m ade mor ediff icu lt byusin g chara cter is tic s of thec o mm u ni ca t ion s me diumfo r th e legitim a te chann elt hat are  n eve r contro l le d or examine d b y leg i t imate user s . Fo r  e x ample , a fi le can  be ope n edan d close d b y a program  in a spe c ifi c,  tim ed patte rn  tha tcan  b e detected by a nother p rogram,a n d thepat t ernc an bein terpreted as  a st ri n g of bi t s , f orminga  co ver t c hann el.  Sin c e it is unlikely that le giti mateu ser s wil l che ck  for pat t erns  of file opening
 this_angle α_becomes too small, it_is not_possible_to top_the_jib further upward_anymore. In such_a situation the multiple_fall topping cable_lies_nearly parallel to the jib. Thus, a higher vertical column of the crane would_permit_the jib_to_be_pivoted further in upward direction_and with this the hoisting_crane can_handle larger objects. A higher vertical column is_also_advantageous during hoisting_when the jib is in a lower, e.g. substantial_horizontal position.
The forces, which occur when_hoisting a heavy_load,_introduce_less tension in the_topping cable, when the hoisting crane_is designed with a bigger angle_α between the topping cables and the_jib, when the jib is in_the horizontal position. Normally in_open sea_there are no difficulties with_the large geometry_of the_hoisting crane, but_a great height of the crane_does effectively limit_the operational area of the vessel_with_such a crane._For_example,_sometimes the_vessel has to_come_close to_a_large building on the quayside, close_to_a drilling rig, or it has to_travel inland and pass_under_a structure like a_bridge. The present invention relates_generally to a method and apparatus_for blocking_access to_an information processing system by an unauthorized user, and more particularly_to such a method and apparatus_where a channel boundary_is employed_to_allow access just_by_legitimate users.
For_purposes of the present invention and its_background, we_consider situations where there is an_information flow boundary that_is_intended to prevent unwanted outward flow_of information from one or more_information technology products while allowing_desired_information_flows. The information flow boundary_is enforced by one or multiple_information technology products_acting as a boundary controller. One possible_function_of a boundary controller is to_prevent_or mitigate covert channels. In information_theory,_a_covert channel is a parasitic_communications channel that draws bandwidth from_another channel in order to transmit information without the_authorization or knowledge_of the latter channel's designer,_owner,_or_operator. A covert channel is so called because it is_hidden within_the medium of_a legitimate communications channel. The detection of a covert channel_can be made more difficult by using_characteristics of the communications medium for the legitimate channel that are_never controlled or examined by legitimate users. For_example, a file can be opened and_closed by a program_in_a specific, timed pattern that can be_detected_by_another_program, and the_pattern can be_interpreted as a_string of_bits, forming a_covert channel._Since it is_unlikely_that legitimate users will check for patterns of file opening