Aa|q  0 U`P 0 @0 p@`@@0HH $ @d HHHH̀̀̀ff@  d Footnote TableFootnote**.\t.\t/ - :;,.!? b0  cNTOCHeading1Heading2   WEquationVariablesSN-::=N.:99;;R<<$monthname> <$daynum>, <$year>"<$monthnum>/<$daynum>/<$shortyear>;<$monthname> <$daynum>, <$year> <$hour>:<$minute00> <$ampm>"<$monthnum>/<$daynum>/<$shortyear><$monthname> <$daynum>, <$year>"<$monthnum>/<$daynum>/<$shortyear> <$fullfilename> <$filename> <$paratext[Title]> <$paratext[Heading1]> <$curpagenum> <$marker1> <$marker2> (Continued)+ (Sheet <$tblsheetnum> of <$tblsheetcount>)Heading & Page <$paratext> on page<$pagenum>Pagepage<$pagenum>See Heading & Page%See <$paratext> on page<$pagenum>. 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It treats the argu0sment as a file name, and returns the protection mode of the file as a short integer. Identify three non-robust fea@2tures of this routine, and state how to fix them. sQ`//* return protection mode of the named file */ ]`short int protmode(void) u`{ w`struct stat stbuf; |`char inbuf[100]; x` ~`gets(&inbuf); y`stat(inbuf, &stbuf); z`return(stbuf.st_mode&0777); {`} t̪`:Define each of the following terms in one short sentence: }`public key cryptosystem `challenge-response ` ciphertext '`end-to-end encryption 0`! principle of fail-safe defaults v`EShow how ACLs and C-Lists are derived from an access control matrix.  pDiscuss the revocation problem with respect to access control lists and capabilities. How might one efficiently A@Jimplement a command to revoke access to an object by one particular user? P Consider the Bell-LaPadula multilevel security model. If a subject with security label ( L ,  C ) can read an object 0\Iwith security label ( L ,  C ), then ( L ,  C ) is said to  dominate  ( L ,  C ). Prove that this  dominates  relation is reflexive, @antisymmetric, and transitive. w qConsider the problem of managing certificates. One expert said that a hierarchical scheme, such as that employed 0pby PEM, is more likely to be used for business than the Web of Trust employed by PGP. What specific features of pthe hierarchical system as implemented for PEM (and for other Internet applications) led him to make this asser@@tion? Why might these features lead him to make this statement?  oWhy is a precise statement of security requirements critical to the determination of whether a given system is @secure? qŪ pSystem vendors often add security features to strengthen the security of their systems. These additions are not pѪndesigned into the system, but rather are added after the system has been shipped. Discuss whether adding secuority features to a large, complex operating system not designed with security in mind (such as the UNIX operatping system or Windows 95) violates any of Saltzers and Schroeders design principles. (Go through all 8 design @ principles.) 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