Clues for al-Kindi

Atbash

a / b / c / d / e / f / g / h / i / j / k / l / m / n / o / p / q / r / s / t / u / v / w / x / y / z
Z / Y / X / W / V / U / T / S / R / Q / P / O / N / M / L / K / J / I / H / G / F / E / D / C / B / A

Code: SV DZH Z EVLB XOVEVL NZM

Answer: he was a very clever man

Homophonic Cipher

Answer: philosopher of the arabs

Pigpen

Use the shapes in the key to spell out the message.

Answer: Musician

Playfair Cipher

Using the 5 x 5 square:

P / L / A / Y / F
I / R / C / H / E
B / D / G / K / M
N / O / Q / S / T
U / V / W / X / Z

The code is YI RP QT NL EI HV

Reverse the procedure to get: ph il os op he rx

Answer: philosopher

Caesar Shift

The code is: BYLUT TKHYNW JXU DYSJX SUDJKHO

Either check all possible 26 shifts (not difficult to do. Just check if the first word is in English as expected, or move on). Or, guess that JXU in the code is the word ‘the’.

It uses a shift of 10 anti-clockwise (that’s 16 clockwise).

Answer: lived during the ninth century

Knapsack Cipher

The code is: 1672 1004 667 1676 1336 667 1005 1339 1342 335 1001 1005 1001 674 1342 1002 669 1002

Multiply each number by 3: 5016, 3012, 2001, 5028, 4008, 2001, 3015, 4017, 4026, 1005, 3003, 3015, 3003, 2022, 4026, 3006, 2007, 3006

And use the last two digits: 16 12 01 28 08 01 15 17 26 05 03 15 03 22 26 06 07 06

Work out the binary instructions to make each number from 1, 2, 5, 10, 20 to find the message.

Answer: Frequency Analysis

Frequency Analysis

a / b / c / d / e / f / g / h / i / j / k / l / m / n / o / p / q / r / s / t / u / v / w / x / y / z
Y / M / N / L / B / T / U / R / S / D / F / G / H / J / Q / W / E / I / A / Z / X / C / K / V / P / O

Answer:the secret codebreaker was a very clever man indeed.

he studied a lot of subjects including mathematics

Affine Cipher

C = 7 because (7 × 15) – 1 = 104 – which is a multiple of 26.

ciphertext: / T / E / Q / F / X / E / X
in numbers: / 19 / 4 / 16 / 5 / 23 / 4 / 23
C(c – B): / 105 / 0 / 84 / 7 / 133 / 0 / 133
remainder: / 1 / 0 / 6 / 7 / 3 / 0 / 3
plaintext: / B / a / g / h / d / a / d

Answer: baghdad

Railfence Cipher

The code uses 45 letters. It could be 3 rows, 5, rows, 9 rows or 15 rows. The answer is 5 rows. The code is then written in columns.

t / h / e / S / e / c / r / e / t
c / o / d / E / b / r / e / a / k
e / r / w / A / s / a / f / a / m
o / u / s / M / u / s / l / i / m
s / c / i / E / n / t / i / s / t

Answer: the secret codebreaker was a famous muslim scientist

Clues for Alan Turing

Dancing Men

Answer: second world war

Dots and Pinpricks

Answer: born in London

Semaphore

Because you are stood behind the flag waver you need to reverse the symbols.

Answer: codebreaker

Pocket Enigma

The code is ZCCZRTVBLBBJKPA

The first word is ‘the’. This means Z becomes t. Turn the pocket enigma until you find Z connected to T – there are two positions where Z becomes T. Turn the rotor one place clockwise to find which of these two options connects C to H. When you have found the correct position turn it one place clockwise to confirm C becomes E as expected.

The rotor starting position is E.

Answer: the bombe machine

Vigenere

The keyword was ENIGMA

E / N / I / G / M / A / E / N / I / G / M / A / E / N / I / G / M / A / E / N / I / G / M / A / E / N
f / a / m / o / u / s / b / r / i / t / i / s / h / m / a / t / h / e / m / a / t / i / c / i / a / n
J / N / U / U / G / S / F / E / Q / Z / U / S / L / Z / I / Z / T / E / Q / N / B / O / O / I / E / A

Answer: famous british mathematician

World War I Cipher

Code: GXXDFXFGFXXADFADGDDFFFFGGGXDAG

Reverse the process. Write the keyword in alphabetical order, with the code written in rows underneath:

e / g / i / r / t
G / X / X / D / F
X / F / G / F / X
X / A / D / F / A
D / G / D / D / F
F / F / F / G / G
G / X / D / A / G

Arrange the columns into the keyword tiger:

t / i / g / e / r
F / X / X / G / D
X / G / F / X / F
A / D / A / X / F
F / D / G / D / D
G / F / F / F / G
G / D / X / G / A

Written in pairs: FX XG DX GF XF AD AX FF DG DD GF FF GG DX GA

These are coordinates using this grid:

A / D / F / G / X
A / q / A / z / w / S
D / x / E / d / c / R
F / f / V / t / g / B
G / y / H / n / u / i/j
X / m / K / l / o / P

Answer: born last century

Error Correcting Codes

The following message contains two mistakes.

0 / 1 / 0 / 0 / 1 / 1
1 / 0 / 0 / 0 / 0 / 1
0 / 0 / 1 / 1 / 0 / 0
0 / 1 / 1 / 0 / 0 / 0
1 / 0 / 1 / 0 / 0 / 1
1 / 0 / 1 / 0 / 0 / 0
1 / 1 / 0 / 0 / 1

Before correction the message seems to say leniss.

Rows 1 and 5 do not add up. And columns 2 and 4 do not add up. Giving four possible wrong numbers.

If the two mistakes were in the same column, (or same row) there would be no column (or row) mistakes. The two mistakes would cancel each other out – proving the two mistakes were in the same column (or row).

So the two mistakes must be in opposite corners of the rectangle made by the four possible wrong numbers.

Changing the numbers in the first row, second column and its opposite on the fifth row, fourth column gives the message: tenifs. Which is not correct.

Changing the numbers in the first row, fourth column and its opposite on the fifth row, second column give the message: genius.

Answer: genius

Morse Code

a / 5 dots / n / 5 dots
b / 9 dots / o / 11 dots
c / 11 dots / p / 11 dots
d / 7 dots / q / 13 dots
e / 1 dot / r / 7 dots
f / 9 dots / s / 5 dots
g / 9 dots / t / 3 dots
h / 7 dots / u / 7 dots
i / 3 dots / v / 9 dots
j / 13 dots / w / 9 dots
k / 9 dots / x / 11 dots
l / 9 dots / y / 13 dots
m / 7 dots / z / 11 dots

The code is

5 dots / 3 dots / 5 dots / 3 dots / 3 dots / 11 dots / 5 dots / 11 dots

Each letter has a number of options.

a / i / a / I / I / c / a / c
n / t / n / t / t / o / n / o
s / s / p / s / p
x / x
z / z

The message is 71 dots. The letters total of 46 dots, with the remainder from the pauses between letters and the space between the two words.

Answer: station x

RSA

Code: 25, 0, 24, 28, 49, 8, 9, 25, 18, 9, 23, 5, 15, 24, 2, 7, 41

Sent using public key E = 27, and m = 55.

If m = 55, the original primes are 5 and 11.

We need to find D such that (E x D) – 1 is a multiple of (5-1)(11-1) = 40.

Use D = 3 (since (27 x 3) – 1 = 80).

Raise the code to the power D = 3: 15625, 0, 13824, 21952, 117649, 512, 729, 15625, 5832, 729, 12167, 125, 3375, 13824, 8, 343, 68921

Find remainder after division by m = 55: {5, 0, 19, 7, 4, 17, 14, 5, 2, 14, 12, 15, 20, 19, 8, 13, 6}

Convert back into letters (a=0, b=1, …, z=25): f a t h e r o f c o m p u t i n g

Answer: computing