• Megan Piorko

Cipher Treasure Hunt Part II: A Secret Key Hidden in Plain Sight

This past summer Sarah Lang (University of Graz) and I set off an exciting adventure that began back in 2019, in a dimly lit bar in Amsterdam, pouring over a mysterious alchemical cipher titled “Marrow of the Hermetic Philosophy”. In our first Jargonium post, we introduced readers to our alchemical quest to uncover the secrets encrypted in the cipher and cipher table at the center of an early modern alchemical notebook written by English polymath John Dee and his son, Arthur Dee.


Since then, our ‘work-in-progress’ on the cipher was published in HistoCrypt 2021. Before the metaphorical ink was dry on the digital publication, our inboxes were filled with emails from computer science scholars promising that their program would be the key to decrypting the cipher (much like the early modern alchemists who promised that their recipe would yield the true Philosophers’ Stone). It was ironic then, when Richard Bean (University of Queensland mathematician and Jules Verne enthusiast) contacted us to say he had successfully decrypted the cipher text in just a few days using a pen and a piece of paper (with the help of Latin statistical models).


Richard Bean's notebook used for decryption

The “Marrow of the Hermetic Philosophy” is a Della Porta style cipher, which can only be decrypted with a secret passphrase that becomes the ‘key’ to the cipher. In searching for the key, we looked everywhere except right in front of our eyes: it was in the alchemical notebook! Much to our simultaneous delight and chagrin, Arthur Dee wrote the passphrase to the cipher on the back of the cipher table. Since we were working with digital reproductions of the pages of the notebook, we didn’t immediately think to “flip the page over”, which would have been a natural inclination if we had the physical manuscript in front of us.

In searching for the key, we looked everywhere except right in front of our eyes: it was in the alchemical notebook! Much to our simultaneous delight and chagrin, Arthur Dee wrote the passphrase to the cipher on the back of the cipher table.
Cipher passphrase written on the reverse side of the cipher table

The extremely long (45 letters!) key to the encrypted text is “sic alter iason aurea felici portabis uellera colcho” [like a new Jason you will carry the Golden Fleece away from the lucky Colchian], in reference to the ancient Greek myth of Jason and the Argonauts. Early modern alchemists used the story of the Golden Fleece as an allegory for making gold and finding the Philsophers’ Stone. However, we used it to decrypt the cipher text.


While we have found the key and cracked the code to the 400-year-old encrypted text of “Marrow of the Hermetic Philosophy” (the discovery is featured in the scholarly news source The Conversation), this alchemical mystery is far from solved. Each clue hidden in this metaphorical recipe for the Philosophers’ Stone leads us down a new path rife with alchemical Decknamen (or cover names) and chemical allegory that require expert interpretation to understand the historical context of alchemy. Since we can’t speak directly with 17th-century alchemist and physician to the Tsar Arthur Dee, we will have to diligently unpack the many layers of encryption and alchemical secrecy obscuring the Philosophers’ Stone.


…to be continued.


In the meantime, readers are invited to try their hand at solving a passage from the encrypted alchemical text.

Transcription of cipher table in MS Sloane 1902 by Megan Piorko
Transcription of cipher text in MS Sloane 1902 by Megan Piorko

Megan Piorko is Allington Postdoctoral Fellow at the Science History Institute in Philadelphia, USA.


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