Codebusters Test Curriculum Framework 3

Question 1

In a columnar transposition cipher, what role does the keyword play in the decryption process?

Accepted Answer

It provides the order in which columns are read to reconstruct the plaintext

Answer

In a columnar transposition cipher, the keyword's alphabetical order determines the sequence in which columns are read during decryption.

Question 2

Which cipher is based on encoding letters as pairs of numbers using a Polybius square?

Accepted Answer

Polybius checkerboard cipher

Answer

The Polybius checkerboard cipher encodes each letter as its row and column coordinates within a 5x5 grid.

Question 3

In the context of Codebusters, what does 'index of coincidence' measure?

Accepted Answer

The probability that two randomly chosen letters in a text are identical

Answer

The index of coincidence measures how likely two randomly selected letters from a text are the same, helping distinguish monoalphabetic from polyalphabetic ciphers.

Question 4

The Kasiski test is used in Codebusters to:

Accepted Answer

Estimate the keyword length of a Vigenère cipher by finding repeated sequences

Answer

The Kasiski test finds repeated trigrams or longer sequences in the ciphertext; the distances between repetitions often share a common factor equal to the keyword length.

Question 5

A Codebusters team encounters a cipher where letters are replaced by symbols from a pigpen-style grid. This is best described as:

Accepted Answer

A symbolic substitution cipher

Answer

Pigpen and similar grid-based ciphers are symbolic substitution ciphers that replace plaintext letters with geometric shapes or symbols.

Codebusters Test Practice Test

Codebusters Test Practice Test

Codebusters Test Curriculum Framework 3