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F;Wa Macro Name d= d= d l d= do  WBm }d = d  <W|aHeadings Table }Hd = Hd  <W}a }Hd = Hd  <W~a }H= H =!Paragraph ForPAmat }HH= HH  =WaHeading Level }H= H  =Wa Comments }H= H >W aTitle }HH= HH  >Wa }H= H  >Wa }KH = KH  ?Wa Heading1 }HKH = HKH  ?Wa }KH = KH  ?Wa }WH = WH  @Wa Heading2 }HWH = HWH  @W a }WH = WH  @W a }cH = cH  AW a }HcH = HcH  AW a }cH = cH  AW a w-Dˏ>w886D}?H =[D #?H F;Wa Replace With }H =]D"$H F;W aHead }H =_D#%H F;W!a Comments }? =aD$&? FCW"a }?H =cD%'?H FCW#a }H =eD&(H FCW$a }H =gD')H FCW%a }d =jD(.d FDW&aCharacter Macros HHˆ;"HHˆ+Ge HHˆ;$3HHˆ**l}?d =lD?d FDW'a }?d =nD?d FDW(a }? =pD)/? FEW)a Macro Name }?H =rD.0?H FEW*a Replace With }H =tD/1H FEW+a Comments }? =vD0B? FFW,a HUV ;.HUV 3Ge HUV ;05+HUV 22l H$ ;1H$ 5Ge H$ ;33H$ 44l HHˆ;4HHˆ= !!7 ` Homework 2 G `Due Date : April 19, 2001 :`Points : 100 H` ! z( 20 points ; text, exercise 1.3) The aphorism security through obscurity says that hiding information provides psome level of security. Please give an example of a situation in which hiding information does not add apprecia@?bly to the security of a system. Give an example when it does. x J( 20 points ; text, exercise 2.5) Let  c  be a copy flag and let a computer system have the set of rights {  r ,  w ,  x ,  a ,  l ,  m ,  @ o  }. #; Using the syntax in class (and in section 2.3 of the text), write a command  copy_all_rights ( p ,  q ,  s ) that cop@Eies all rights that  p  has over  s  to  q .  fModify your command so only those rights with an associated copy flag are copied. The new copy should  @not  have the copy flag. 4ƪ`J( 40 points ; text, exercise 3.1) Prove or give a counterexample: 5*Ҫ hThe predicate  can  share ( a ,  x ,  y ,  G 0 ) is true  if and only if there is an edge from  x  to  y  in  G 0  labelled  a , or if the UU@following hold simultaneously: 64 \ hVthere is a vertex  with an  s -to- y  edge labelled  a ; 7j`|there is a subject vertex  x  such that  x  =  x  or  x  initially spans to  x ; 8 j`there is a subject vertex  s  such that  s  =  s  or  s  terminally spans to  s ; and 9* Uthere is a sequence of subjects  x  =  x 1 , ,  x n  =  s  with  x i  and  x i +1  (1  i  <  n ) being connected by an edge UU$?@Alabelled  t , an edge labelled  g , or a bridge. 6? }( 20 points ; text, exercise 4.5) Classify each of the following as examples of mandatory, discretionary, or originaB?@Htor controlled policies, or a combination. Please justify your answers. 1`AThe file access control mechanisms of the UNIX operating system. 2`QA system in which no memorandum can be distributed without the authors consent. 3`?A facility in which only generals can enter a particular room. a< oA universitys registrar office, in which faculty can see grades of a particular student provided that student @has given written permission. HHˆ;6HHˆ66 laL42q>x!aL42qaL42qje4'@in[char[(*W"Bold"W*)s],indexes[0,1,char[G],num[0.00000000,"0"]]] d;;<@H$ ;<;>H$ == l H$ ;=;H$ <Wh6April 10, 2001ECS 253 Spring 2001Page 1  HUV ;>;<@HUV ?? l HUV ;?;HUV >Wh@Last modified at  10:01 pm on Tuesday, April 17, 2001  HHˆ;@;>HHˆAA l HHˆ;A;HHˆ@W` }?H =xD1C?H FFW-a }H =zDBH FFW.a d=~EEd=DdFF l d=DdRCERUX[^adgjmpsvy| %).1dLeftd;Rightd ReferenceddHTMLdDHTMLd Headings@@ `Mapping Table Title. @@ `Body.  f@P`TitleBody. f@E ` Numbered1.\tNumbered. @@ `Footer. f@T ` TableTitleT:Table : . f@ `. 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DateProject. @@ `Header Double Line. f@T `Heading1Body. f@ ` NumberedSpaced. f@E ` Numbered1.\tNumbered. f@ `.Reading.  f@P`TitleBody. f@$`.Line Single Line. f@ `CellBody. f@ ` CellHeading. f@ ` Footnote. f@T `Heading2Body. f@T ` HeadingRunInBody. f@ ` TableFootnote. f@T ` TableTitleT:Table : . f@ ` Numbered.\t. f@ ` Numbered.\t. f@ ` NumberedSpaced. ` `` ` 9 ` ڝ``Emphasis ``EquationVariables ڝ` 9  BoldItalic `Italic `Bold `9 ` ` ` Subscript ` Subscript # Fixed \ symbol `Normal ZZThinMediumDoubleThick@ Very Thin HHHHHFormat AH Mapping Table HHHHHFormat BH Mapping Tableh*|#HHHHHf$*DHH+5?HH&69?HH :C?HHH DF?HH*6 ? @ h( A B C D E h  F G H I J h  K L M N O h  P Q R S T h( UVWXYh Z[\]^h_`abc7h defghChijklm]h(nopqrh stuvwh xyz{|h(}~h h    h  h h h)h  !"#$5h%&'()Oh  *+,-.[h!/ 0 1 2 3 uh "4!5!6!7!8!h!#9":";"<"="©h ">#?#@#A#B#» %C$D$E$ $&F%G%H% %'I&J&K& &(L'M'N'')O(P(Q(((*FR)S)T)D )FU*V*W*V ,FX+Y+Z+f +-F[,\,],r ,.F^-_-`-~ -/Fa.b.c..0Fd/e/f//1Fg0h0i002Fj1k1l113Fm2n2o224Fp3q3r3 35Fs4t4u4& 4Fv5w5x58 7Fy6z6{6H 68F|7}7~7T79F888n 8F999 ;F:::: :CF ;";#;$; =  <<<<> ====? >>>K >@ ???W ?A @@@c @ AAA ;F%C&C'C(C EF)D,D-D DFF.E/E0E EF1FBFCFComment ;C ;Gd BlackT!WhiteddARedddGreendd BluedCyandMagentad YellowHeader/Footer $1Header/Footer $1Header/Footer $2Header/Footer $2IndexIndexCommentCommentSubjectSubjectAuthorAuthorGlossaryGlossaryEquationEquation Hypertext Hypertext  Cross-Ref Cross-Ref Conditional TextConditional TextPositionFMPrivatePositionFMPrivateRangeEndFMPrivateRangeEndFMPrivate HTML Macro HTML Macro M.Times.P Times-Roman FrameRoman M.Times.B Times-Bold FrameRoman M.Helvetica.BHelvetica-Bold FrameRomanM.Helvetica.BIHelvetica-BoldOblique FrameRoman M.Times.I Times-Italic FrameRoman M.Courier.PCourier FrameRoman M.Symbol.PSymbol FrameRomann"Courier8 Helvetica[Symbol_Times#Regular$Roman MediumBoldRegular ObliqueItalicȕ( h{ޱzusN+,^i* IGΪq{Y$OGm;zOh(]dӒ/2`H aIC64/<1(en-Aa