Codebusters Test Graduation Requirements 4

Question 1

In Codebusters, what does it mean when a cipher is labeled 'K1' in the key phrase system?

Accepted Answer

The keyword is placed starting at letter A in the plaintext alphabet

Answer

A K1 keyphrase places the keyword at the start of the plaintext alphabet, building the cipher alphabet from that rearranged sequence.

Question 2

What is the graduation requirement for understanding 'Morbit' cipher used in advanced Codebusters events?

Accepted Answer

A cipher using Morse code fragments encoded with a key

Answer

The Morbit cipher encodes Morse code dot-dash sequences using a keyed 9-symbol alphabet, making it a variant of fractionated Morse.

Question 3

Which technique is a graduation requirement for cracking the columnar transposition cipher?

Accepted Answer

Anagramming columns to find readable digrams

Answer

Columnar transposition is broken by rearranging cipher columns until adjacent pairs produce high-frequency English digrams like TH, HE, and IN.

Question 4

For Codebusters graduation at the invitational level, which of these cipher types is students are NOT required to encode (only decode)?

Accepted Answer

Porta cipher

Answer

The Porta cipher is a complex polyalphabetic cipher not required at invitational level; students focus on decoding simpler ciphers there.

Question 5

What graduation skill involves using the 'unicity distance' concept to determine when enough ciphertext exists to uniquely solve a cipher?

Accepted Answer

Information theory application to cryptanalysis

Answer

Unicity distance is an information theory concept defining the minimum ciphertext length needed to uniquely determine the key with no ambiguity.

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