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The correct option is (a) Dot duration

Easy EXPLANATION - Dot duration is the basic unit of time measurement in Morse CODE TRANSMISSION. Both dot and DASH SIGNAL are used as time measurement in Morse code.

Right option is (a) Samuel F. B. Morse

Best EXPLANATION: Morse Code is named after Samuel F. B. Morse who is the inventor of the telegraph. The best FIRST search algorithm USING heuristic evaluation rule or FUNCTION was proposed by an Israeli – American computer scientist and philosopher JUDEA Pearl.

Right OPTION is (a) DASH

To explain: The two signal DURATION used in Morse code are Dot and Dash. They are also called Dits and DAHS. While other symbols are expressed in terms of dots and dash.

Right choice is (d) 3 Units

The explanation is: In Morse Code, the LENGTH of the SINGLE DOT is defined to be 1 Unit. While dash is defined to be 3 Unit. In Morse Code, the space between words is 7 unit.

The CORRECT option is (c) KVK

Easiest explanation - The decryption in bifid cipher begins IDENTICALLY to encryption. Then we find the corresponding coordinates and then we get the plain text. So the plain text is “KVK”.

The correct answer is (d) YFSGWNFBW

Explanation: For encrypting the plain text using bifid CIPHER we first form the polybius square with the HELP of given key. After this, the plain text is divided into BLOCKS of length 5 and corresponding coordinates are NOTED. So the corresponding cipher text would be “YFSGWNFBW”.

The correct choice is (b) PLNSOWGKQM

Easy explanation - For ENCRYPTING the plain text using BIFID CIPHER we first form the polybius SQUARE with the help of given key. After this, the plain text is divided into blocks of length 5 and CORRESPONDING coordinates are noted. So the corresponding cipher text would be “PLNSOWGKQM”.

Right answer is (B) false

For EXPLANATION: Bifid SQUARE COMBINES polybius square with TRANSPOSITION. So the given statement is false.

Correct choice is (b) false

The best I can EXPLAIN: Trifid CIPHER is a variation of BIFID cipher. The only difference between them is that trifid cipher uses a 3×3 KEY SQUARE instead of 5×5 square.

The correct answer is (a) bifid cipher

Easiest EXPLANATION - Bifid cipher uses POLYBIUS square for ENCRYPTING the PLAIN text. Bifid cipher combines polybius square cipher with TRANSPOSITION.

The correct answer is (a) length of BLOCKS in which the plain text is divided before encryption

The best EXPLANATION: POLYBIUS SQUARE is similar to substitution cipher. It is also KNOWN by the name of Polybius checkboard.

Right choice is (b) QWERTY

Easy explanation - RUNNING KEY cipher is a TYPE of poly alphabetic SUBSTITUTION which uses tabula recta for MAKING substitutions in the plain text. Using the table we find the plain text to be “QWERTY”.

Right choice is (a) GNPJIJBQRR

For explanation: ENCRYPTION in running KEY cipher TAKES place exactly as in vigenere cipher if we don’t INCLUDE the indicator block. So by using the tabula recta we can find the ENCRYPTED text which is “GNPJIJBQRR”.

Correct answer is (a) vigenere CIPHER

Best explanation: Vigenere cipher is a variation of vigenere cipher. The only difference between them is that in vigenere cipher a RANDOM KEY is chosen WHEREAS in running key cipher key is chosen from a book or a text.

Right option is (b) false

To explain: RUNNING key cipher is a POLY alphabetic SUBSTITUTION cipher. Encryption is DONE by using TABULA recta.

The correct choice is (a) SECRET

Easiest explanation - Running key cipher is a type of poly ALPHABETIC SUBSTITUTION which uses tabula RECTA for MAKING substitutions in the plain text. Using the table we find the plain text to be “SECRET”.

The correct option is (a) true

Explanation: Keyword cipher is less SECURE than running key cipher. It is due to the FACT that keyword cipher is mono ALPHABETIC and thus can be cracked using frequency ANALYSIS. But running key cipher being a poly alphabetic cipher is harder to crack.

Right ANSWER is (a) 26 rows and 26 columns

Easy EXPLANATION - Encryption of plain TEXT using running key cipher is done by making USE of tabula recta. It consists of 26 rows and 26 columns which have ALPHABETS written 26 times. These are shifted towards left after each row.

The correct choice is (c) running key cipher

The EXPLANATION is: Running key cipher is a poly ALPHABETIC cipher. It USES a key book or key text instead of a KEYWORD which is agreed by both PARTIES before encryption takes place.

Correct ANSWER is (c) tabula RECTA

The BEST explanation: Encryption of plain text in RUNNING key cipher is done by making use of tabula recta. The same table is also USED for encryption in vigenere cipher.

Correct choice is (b) poly-ALPHABETIC cipher

The explanation is: Running key cipher is a SUBSTITUTION cipher. It falls under the category of poly alphabetic cipher as it uses MULTIPLE substitutions at different positions in order to cipher the PLAIN text.

The correct choice is (c) it gives INFORMATION regarding the book/text from where the KEY is taken

Best explanation: The purpose of having an indicator block in running key cipher is to GIVE information to the receiver about the source of a key being used. It is USUALLY included in the second last block of the message.

The correct answer is (a) 431133

The BEST EXPLANATION: For encrypting using polybius square cipher we have to use the table which is shown below and write (row, col) coordinates corresponding to each letter.

1 2 3 4 5

1 A B C D E

2 F G H I/J K

3 L M N O P

4 Q R S T U

5 V W X Y Z

So the ciphered text will be “431133”.

The correct choice is (b) CSK

For explanation: For decoding ciphered text we have to USE the polybius SQUARE in and find out the letters corresponding to each pair of coordinate. So in this case the PLAIN text is FOUND to be “CSK”.

The correct answer is (c) ADFGVX cipher

Easy explanation - ADFGVX cipher uses POLYBIUS square cipher in its FIRST STEP of encrypting DATA. It uses a 6 X 6 version of polybius square.

The correct OPTION is (b) false

The explanation is: Polybius square cipher is CLOSELY RELATED to mono alphabetic cipher. Thus it is quite vulnerable to FREQUENCY analysis MUCH like any other mono alphabetic cipher.

The correct choice is (a) true

Easiest explanation - Polybius SQUARE is CLOSELY related to MONO alphabetic substitution CIPHER and thus is more vulnerable to frequency analysis. Whereas polybius square being a poly alphabetic cipher is less vulnerable to frequency analysis and so is more secure.

The correct option is (C) I and J

The best explanation: The usual size of poybius SQUARE for encrypting English ALPHABETS is 5 X 5. Usually, I and J are combined so as to fit all English LETTERS in this table.

The correct option is (a) MONO-alphabetic CIPHER

Best EXPLANATION: Polybius square cipher is much like any mono alphabetic cipher. It is because it applies a fixed SUBSTITUTION to the letters present in plain TEXT.

The correct choice is (a) 5 X 5

For explanation: The usual size of poybius square for ENCRYPTING English alphabets is 5 X 5. Usually, I and J are COMBINED so as to fit all English letters in this table.

The correct ANSWER is (a) To represent the plain text by smaller set of symbols

Explanation: Polybius SQUARE is SIMILAR to substitution cipher. Polybius square allows us to cipher the plain text in such a way that a minimum NUMBER of symbols are used in the ENCRYPTED text.

The correct option is (c) 2

Explanation: ASYMMETRIC cipher makes USE of 2 keys for the PURPOSE of encryption. ONE is known as public key whereas other is called PRIVATE key.

Correct answer is (b) RUSSIA

Easiest EXPLANATION - Trithemius CIPHER is a TYPE of poly alphabetic SUBSTITUTION which uses tabula recta for making substitutions in the plain text. Using the table and using the key as ABCDEFGHIJKLMNOPQRSTUVWXYZ we find the plain text to be “RUSSIA”.

The correct answer is (a) SBPISZTKZH

Best explanation: Encryption in trithemius CIPHER takes place exactly as in VIGENERE cipher if we CONSIDER the key to be ABCDEFGHIJKLMNOPQRSTUVWXYZ. So by using the tabula recta we can FIND the ENCRYPTED text which is “SBPISZTKZH”.

Right answer is (c) trithemius cipher

The best explanation: Trithemius cipher is a special case of vigenere cipher and RUNNING key cipher is a variation of vigenere cipher. If ONE FIGURES out that the cipher being used is trithemius then it is very easy to crack, UNLIKE running key and vigenere ciphers as these use a SECRET key for encryption.

Correct CHOICE is (a) True

Easy explanation - TRITHEMIUS cipher uses a more COMPLEX VERSION of caesar cipher. So trithemius cipher is HARDER to crack as compared to caesar cipher.

The CORRECT answer is (a) ABACUS

For explanation: Running key cipher is a TYPE of POLY alphabetic substitution which USES tabula recta for making SUBSTITUTIONS in the plain text. Using the table and key as ABCDEFGHIJKLMNOPQRSTUVWXYZ we find the plain text to be “ABACUS”.

Right OPTION is (b) false

The explanation is: Trithemius CIPHER is a special CASE of vigenere cipher with ABCDEFGHIJKLMNOPQRSTUVWXYZ as key. So trithemius cipher is easier to crack as the key being used remains same every time.

Correct option is (b) vigenere cipher

The explanation is: Trithemius cipher is a special case of vigenere cipher. The DIFFERENCE is that vigenere cipher USES a different key EVERY TIME but a fixed key is used by trithemius cipher.

The correct answer is (d) trithemius cipher

Explanation: Ciphers LIKE running key cipher, vigenere cipher, trithemius cipher, etc. makes use of TABULA recta. WHEREAS hill cipher, rail fence cipher and ROUTE cipher does not require tabula recta for encryption of plain TEXT.

Correct ANSWER is (d) TRITHEMIUS cipher

The best explanation: If in caesar cipher we consider a shift that increases by 1 by each LETTER starting at 0 then it is EQUIVALENT to trithemius cipher. So trithemius cipher is a special case of caesar cipher.

Correct answer is (C) tabula recta

Best explanation: Encryption of plain text in trithemius cipher is DONE by MAKING use of tabula recta. The same table is also USED for encryption in VIGENERE cipher and running key cipher.

The correct option is (B) POLY-alphabetic cipher

Easiest explanation - Trithemius cipher is a substitution cipher. It falls under the CATEGORY of poly alphabetic cipher as it uses multiple substitutions at different positions in ORDER to cipher the plain text.