[Janelle Ward]

You might have accepted the challenge, thrown out in the Forum, to break the code on a new 50-cent coin released last week.

The coin was released by the Australian Signal’s Directorate (ASD) to commemorate its 75th anniversary.

University of Queensland research fellow Dr Richard Bean has cracked more than a few historical cryptograms.

On the scale of challenging codes, he said the code was relatively simple for those with some experience.

“It’s not designed to be super challenging,” he said.

So how do you crack it?

The coin might look daunting at first, but most code crackers would start at the simplest point — the six braille numbers around Queen Elizabeth II.

They spell “Atbash”, one of the most common tools for cracking codes using a simple reverse-order alphabet.

This gives a clue as to solving the characters around the rim on the other side, replacing A for Z, B for Y and so on.

Applying it to the outer circle results in:

“We are audacious in concept and meticulous in execution. Find clarity in 7 width x 5 depth.”

Now stay with us, it’s about to get a bit more complicated.

This is where a pen and paper come in handy.

The 7×5 part is an instruction to arrange the inner rim of letters in grids of rows of seven, starting from BGOAMVO at the bottom of the coin and continuing on around the coin.

There are 70 letters, so they need to be arranged in two grids of 35 letters with five columns.

The two grids are then read from top to bottom to give the message:

“Belonging to a great team striving for excellence we make a difference XOR HEX A5D75.”

Still with us?

The next part is where Dr Bean says he faced the biggest challenge — attempting to decipher the block of letters and numbers in the bottom right third wedge.

The “XOR HEX A5D75” at the end of the last answer is the clue for this next step, and it requires a fair bit of code-breaking know-how.

XOR is a common and highly secure type of encryption, creating sequences of letters and numbers using binary digits.

Without a key, it’s pretty much impossible to crack, and that is why it’s a common defence in encryption software.

Fortunately, the key is “A5D75” and the “hex” means it’s in hexadecimal form, or there are 16 different characters. Solving this one by hand is almost so tedious that it’s pointless.

Or you can put the slab of letters into an online program like Cyber Chef, with the key, and it’ll give you the answer:

“For 75 years the Australian Signals Directorate has brought together people with the skills, adaptability and imagination to operate in the slim area between the difficult and the impossible”.

How each letter is shaded will give you a clue to decipher the final puzzle.(Supplied: Royal Australian Mint)

The last code involves the shading of the two rings of characters. The inner one is in binary — so unshaded is a 0, shaded is a 1 and can be decoded to mean “ASDCbr2022”.

The outer ring is in Morse code, and results in “1947 DS Albert Park”.

They’re both nods to the ASD.

So what’s the point?

It’s all about lifting profiles.

Dr Bean said the idea was to plant the seed in the minds of those who might be interested in a career with the ASD or ASIO.

Were you able to follow that explanation? Are you going to apply for a job with the ASD?

Source: ABC

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