1)Â Â Â Â Â If an attacker has a copy of the cipher text and its content yields no information at all with regard to the plain text message, the text is considered _____________.
a)Â Â Â Â Â cipher perfect
b)Â Â Â Â Â third-eye blind
c)Â Â Â Â Â perfectly secure
d)Â Â Â Â Â third-party secure
Reason:
2)Â Â Â Â Â Which is not a weakness of a shift cipher? _________________________
a)Â Â Â Â Â Once you have the code book you can decode the message.
b)Â Â Â Â Â Natural language letter frequency makes them easy to decode.
c)Â Â Â Â Â The number of letters in the alphabet makes them easy to decode.
d)Â Â Â Â Â Once the shift is determined the message is decoded almost instantly.
Reason:
3)Â Â Â Â Â Quantum cryptography is based on the physics of light. True/False,
Reason with details:
Â
4)Â Â Â Â Â Claude Shannon presented the encryption design principles of _________________.
a)Â Â Â Â Â multiplication and factoring
b)Â Â Â Â Â exponentiation and Logarithms
c)Â Â Â Â Â confusion and diffusion
d)Â Â Â Â Â perplexion and reflection
Reason with how and why it helps encryption:
5)Â Â Â Â Â Two numbers are said to be congruent if _____________________.
a)Â Â Â Â Â one is a multiple of the other
b)Â Â Â Â Â they produce the same remainder after modulo division
c)Â Â Â Â Â they have the same prime number as a factor
d)Â Â Â Â Â they are quotients of the same number
Reason:
6)Â Â Â Â Â A good hash function creates _________ mapping between the source string and the output string.
a)Â Â Â Â Â complex
b)Â Â Â Â Â as many as needed
c)Â Â Â Â Â divisional
d)Â Â Â Â Â one to one
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Reason why it is good:
7)Â Â Â Â Â A number is relatively prime to another if they _____________.
a)Â Â Â Â Â have only each other as factors
b)Â Â Â Â Â have no prime factors in common
c)Â Â Â Â Â only have one prime factor in common
d)Â Â Â Â Â are both divisible by 7
Reason : Â
8)Â Â Â Â Â (15 pts) The following is a ciphertext:
a)     U GIRJ CFJ SWAY. SWAY UR JQW GUCB-TUDDWY. SWAY UR JQW DUJJDW-BWAJQ JQAJ LYUCPR JFJAD FLDUJWYAJUFC. U NUDD SAKW GM SWAY. U NUDD EWYGUJ UJ JF EARR FOWY GW ACB JQYFIPQ GW. ACB NQWC UJ QAR PFCW EARJ U NUDD JIYC JQW UCCWY WMW JF RWW UJR EAJQ. NQWYW JQW SWAY QAR PFCW JQWYW NUDD LW CFJQUCP. FCDM U NUDD YWGAUC – SYACT QWYLWY
b)Â Â Â Â Â What kind of cipher text is this? Mono- or Poly alphabetic; Hint: assume one and when that does not work look for the other
c)Â Â Â Â Â Describe your cryptanalysis process. Show all the steps you went through to decrypt the message. The steps should be in sufficient details so that a reader would be able to decrypt the encrypted text without needing any help from you. Â
d)Â Â Â Â Â If you did find solution somehow please show steps as if you are trying to find the solution. So I know you have exercised your knowledge
e)Â Â Â Â Â State the plain text message.
f)Â Â Â Â Â Â List features of the cipher- text that hindered and helped your decryption process. mention of helpful and hindering features
Note: Only a decrypted message even if it is correct without the methodology and the detailed description of the self-explanatory steps used to decrypt, would not get points.
