Codebusters Test Codebusters Transposition Ciphers 2

Question 1

In a keyword columnar transposition with the keyword BAND, in what order are the columns extracted?

Accepted Answer

2, 1, 4, 3 (alphabetical order: A, B, D, N)

Answer

1, 2, 3, 4 (left to right)

Answer

4, 1, 3, 2

Answer

3, 4, 1, 2

Question 2

What is a double transposition cipher?

Accepted Answer

A cipher that applies two separate transposition operations to the plaintext in sequence

Answer

A cipher that applies one transposition and one substitution step

Answer

A transposition cipher that uses two different keywords simultaneously

Answer

A cipher that transposes the ciphertext back to produce the final output

Question 3

When cryptanalyzing an unknown transposition cipher, what is a productive first step after confirming high IC?

Accepted Answer

Test different column counts by arranging ciphertext into grids and examining column-pair digraph frequencies

Answer

Apply the Vigenère decryption algorithm with trial keys

Answer

Search for the keyword by comparing ciphertext to a dictionary

Answer

Apply the Caesar shift for each of the 26 possible values

Question 4

With a 3-rail fence cipher, what is the pattern of rail assignments for successive letters?

Accepted Answer

1, 2, 3, 2, 1, 2, 3, 2, 1…

Answer

1, 2, 3, 1, 2, 3, 1, 2, 3…

Answer

1, 1, 2, 2, 3, 3, 1, 1, 2…

Answer

1, 3, 2, 1, 3, 2, 1, 3, 2…

Question 5

What does it mean when the last row of a columnar transposition grid is incomplete?

Accepted Answer

Some columns contain one fewer letter than others, which constrains how many letters can be in each column

Answer

The cipher is automatically padded with the letter X

Answer

The keyword length must equal the message length

Answer

Decryption is impossible without additional information

Question 6

Which cipher did the Union Army use extensively during the American Civil War as a military field cipher?

Accepted Answer

The route transposition cipher

Answer

The Vigenère cipher

Answer

The Caesar cipher

Answer

The Playfair cipher

Question 7

In a rail fence cipher, how do you decrypt a ciphertext if you know there are 2 rails?

Accepted Answer

Calculate the length of each rail, split the ciphertext accordingly, and interleave the two groups in zigzag order

Answer

Reverse the ciphertext and apply frequency analysis

Answer

XOR the ciphertext with a binary key derived from the rail count

Answer

Apply the Caesar shift of 2 to every other letter