C839 Introduction to Cryptography Questions And Answers.
Cryptography - answer;-The science of altering communication so that it cannot be
understood without having the key.
cipher - answer;-The algorithm(s) needed to encrypt and decrypt a message.
Mono-alphabet substitution - answer;-Substitute one character of cipher text for each
character of plain text.
Caesar cipher - answer;-Every letter is shifted a fixed number of spaces to the left or the
right in the alphabet.
Ciphertext - answer;-The resultant text after being subjected to the algorithm and key.
Atbash Cipher - answer;-Reverses the alphabet ( A becomes Z, B becomes Y ... ) -
Mono-Alphabet Substitution Cipher. Hebrew code.
Affine Cipher - answer;-single substitution cipher. Each letter is mapped to a numerical
value, permuted with a math function and then converted back to a letter.
Affine cipher formula - answer;-ax + b (mod M)
ROT13 - answer;-One type of substitution cipher in which the entire alphabet is rotated
13 characters.
Scytale - answer;-Physical cylinder used to encrypt messages. Turning the cylinder
produced different ciphers.
Single substitution weaknesses - answer;-Preserve the underlying letter and word
frequency. A low-end PC is more than enough to brute force crack a single sub cipher.
Multi-Alphabet Substitution - answer;-Rotates through various keys.
Cipher disk - answer;-a physical device used to encrypt. Invented by Leon Alberti in
1466. The cipher disk was polyalphabetic; each time you turned the disk, you used a
new cipher.
Vignere cipher - answer;-Invented in 1553 by Giovan Battista Bellaso. A method of
encrypting text by applying a series of different mono-alphabet ciphers based on the
letters of a keyword.
Playfair Cipher - answer;-Invented by Charles Wheatstone in mid 1800s. Lord Playfair
pushed use of it. Uses a 5x5 table and a key word. Rest of the alphabet is placed on
table in alphabetic order, skipping letters used in the keyword. You break up the
message into two character chunks and return a single character value. If the letters
appear on the same row of your table, replace them with the letters to the right. If it is on
the same column, replace them with the letters below.
, C839 Introduction to Cryptography Questions And Answers.
ADFGX Cipher - answer;-First cipher used by the German army during WWI. Uses a
modified Polybus 6 x 6 square. Single columnar transposition, 36 letter alphabet.
Polybus square - answer;-A 6 x 6 square, used by the ADFGVX cipher. The letters
ADFGVX are used as coordinates for the square.
Homophonic substitution - answer;-attempt to make substitution ciphers more robust by
masking the letter frequencies.
nomenclator - answer;-Combines a codebook that had a table of homophonic
substitutions.
Null cipher - answer;-Hiding the message in unrelated plaintext, and using a
prearranged pattern to take certain letters from the plaintext to uncover the true
message.
Book cipher - answer;-Both parties agree to use a particular book as the basis. Then
send coordinates for words.
Rail Fence Cipher - answer;-Encrypt a message by altering each letter on a different
row. then write down the text reading from left to right. The recipient writes the text on
two rows, then reconstructs the message.
The Enigma Machine - answer;-Electro-mechanical cipher machine used to decode
messages. This machine was used mostly by Nazi Germany When the operator
pressed a key the encrypted cipher text for that plaintext was different every time.
TypeX - answer;-British cipher machine used in WWII. Similar to Enigma but with
improvements and more security.
SIGABA - answer;-Rotor machine used by the United States through World War II into
the 1950s. Similar to Enigma but with improvements and more security.
Cryptanalysis - answer;-The study of techniques for attempting to defeat cryptographic
techniques and, and attempt to derive the key.
Frequency Analysis - answer;-Tool for breaking most classical ciphers by examining the
ciphertext looking for frequencies of letter combinations.
Kasiski Method - answer;-A method of attacking polyalphabetic substitution ciphers,
such as Vignere. It's used to try to discover patterns and use that information to decrypt
the cipher.
, C839 Introduction to Cryptography Questions And Answers.
Kerckhoff's Principle - answer;-Only the key protects the encrypted information. A
cryptosystem should be secure even if everything about the system, except the key, is
publicly known.
Symmetric algorithm - answer;-Uses the same key to encrypt and decrypt the message.
Asymmetric algorithm - answer;-Uses two keys, a public and a private key. Also known
as public-key encryption.
symmetric encryption formula - answer;-C=E(k,p)
symmetric decryption formula - answer;-P = E(k,c)
Claude Shannon - answer;-Created information theory in 1949
Substitution - answer;-changing some part of the plaintext for some matching part of the
ciphertext.
Transposition - answer;-Swapping of blocks of ciphertext.
Binary AND - answer;-If both numbers have a one in the same place, then the resultant
number is a one. If not then it is a zero
1st number - 1100
2nd number - 0100
--------------------------
Result - 0100
Binary OR - answer;-Checks to see if there is a one in either or both numbers in the
same place. If so, the resultant number is one, if not, it is zero.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1100
Binary XOR - answer;-Asks if there is a 1 in one of the numbers, but not in both. And it's
reversible.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1011
Block cipher - answer;-a method of encryption that processes blocks of data
Cryptography - answer;-The science of altering communication so that it cannot be
understood without having the key.
cipher - answer;-The algorithm(s) needed to encrypt and decrypt a message.
Mono-alphabet substitution - answer;-Substitute one character of cipher text for each
character of plain text.
Caesar cipher - answer;-Every letter is shifted a fixed number of spaces to the left or the
right in the alphabet.
Ciphertext - answer;-The resultant text after being subjected to the algorithm and key.
Atbash Cipher - answer;-Reverses the alphabet ( A becomes Z, B becomes Y ... ) -
Mono-Alphabet Substitution Cipher. Hebrew code.
Affine Cipher - answer;-single substitution cipher. Each letter is mapped to a numerical
value, permuted with a math function and then converted back to a letter.
Affine cipher formula - answer;-ax + b (mod M)
ROT13 - answer;-One type of substitution cipher in which the entire alphabet is rotated
13 characters.
Scytale - answer;-Physical cylinder used to encrypt messages. Turning the cylinder
produced different ciphers.
Single substitution weaknesses - answer;-Preserve the underlying letter and word
frequency. A low-end PC is more than enough to brute force crack a single sub cipher.
Multi-Alphabet Substitution - answer;-Rotates through various keys.
Cipher disk - answer;-a physical device used to encrypt. Invented by Leon Alberti in
1466. The cipher disk was polyalphabetic; each time you turned the disk, you used a
new cipher.
Vignere cipher - answer;-Invented in 1553 by Giovan Battista Bellaso. A method of
encrypting text by applying a series of different mono-alphabet ciphers based on the
letters of a keyword.
Playfair Cipher - answer;-Invented by Charles Wheatstone in mid 1800s. Lord Playfair
pushed use of it. Uses a 5x5 table and a key word. Rest of the alphabet is placed on
table in alphabetic order, skipping letters used in the keyword. You break up the
message into two character chunks and return a single character value. If the letters
appear on the same row of your table, replace them with the letters to the right. If it is on
the same column, replace them with the letters below.
, C839 Introduction to Cryptography Questions And Answers.
ADFGX Cipher - answer;-First cipher used by the German army during WWI. Uses a
modified Polybus 6 x 6 square. Single columnar transposition, 36 letter alphabet.
Polybus square - answer;-A 6 x 6 square, used by the ADFGVX cipher. The letters
ADFGVX are used as coordinates for the square.
Homophonic substitution - answer;-attempt to make substitution ciphers more robust by
masking the letter frequencies.
nomenclator - answer;-Combines a codebook that had a table of homophonic
substitutions.
Null cipher - answer;-Hiding the message in unrelated plaintext, and using a
prearranged pattern to take certain letters from the plaintext to uncover the true
message.
Book cipher - answer;-Both parties agree to use a particular book as the basis. Then
send coordinates for words.
Rail Fence Cipher - answer;-Encrypt a message by altering each letter on a different
row. then write down the text reading from left to right. The recipient writes the text on
two rows, then reconstructs the message.
The Enigma Machine - answer;-Electro-mechanical cipher machine used to decode
messages. This machine was used mostly by Nazi Germany When the operator
pressed a key the encrypted cipher text for that plaintext was different every time.
TypeX - answer;-British cipher machine used in WWII. Similar to Enigma but with
improvements and more security.
SIGABA - answer;-Rotor machine used by the United States through World War II into
the 1950s. Similar to Enigma but with improvements and more security.
Cryptanalysis - answer;-The study of techniques for attempting to defeat cryptographic
techniques and, and attempt to derive the key.
Frequency Analysis - answer;-Tool for breaking most classical ciphers by examining the
ciphertext looking for frequencies of letter combinations.
Kasiski Method - answer;-A method of attacking polyalphabetic substitution ciphers,
such as Vignere. It's used to try to discover patterns and use that information to decrypt
the cipher.
, C839 Introduction to Cryptography Questions And Answers.
Kerckhoff's Principle - answer;-Only the key protects the encrypted information. A
cryptosystem should be secure even if everything about the system, except the key, is
publicly known.
Symmetric algorithm - answer;-Uses the same key to encrypt and decrypt the message.
Asymmetric algorithm - answer;-Uses two keys, a public and a private key. Also known
as public-key encryption.
symmetric encryption formula - answer;-C=E(k,p)
symmetric decryption formula - answer;-P = E(k,c)
Claude Shannon - answer;-Created information theory in 1949
Substitution - answer;-changing some part of the plaintext for some matching part of the
ciphertext.
Transposition - answer;-Swapping of blocks of ciphertext.
Binary AND - answer;-If both numbers have a one in the same place, then the resultant
number is a one. If not then it is a zero
1st number - 1100
2nd number - 0100
--------------------------
Result - 0100
Binary OR - answer;-Checks to see if there is a one in either or both numbers in the
same place. If so, the resultant number is one, if not, it is zero.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1100
Binary XOR - answer;-Asks if there is a 1 in one of the numbers, but not in both. And it's
reversible.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1011
Block cipher - answer;-a method of encryption that processes blocks of data
