Renaissance Ciphers: Encryption and Eggshells
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Author: Alexander Nowell
Title: Catechismus, sive prima institutio, disciplinaque pietatis Christianae (London, 1572)
Shelfmark: D.15.3 (catalogue record)
Author: Alexander Nowell
Title: Catechismus, sive prima institutio, disciplinaque pietatis Christianae (London, 1572)
Shelfmark: D.15.3 (catalogue record)
![<b>Author:</b> Giambattista della Porta <br>
<b>Title:</b><i> De occultis literarum
</i> [On the concealment of letters] (Montbeliard, 1593)<br>
<b>Shelfmark:</b> S.3.26 <a href="http://idiscover.lib.cam.ac.uk/primo-explore/fulldisplay?docid=44CAM_ALMA21413388950003606&context=L&vid=44CAM_PROD&search_scope=SCOP_QUE&tab=cam_lib_coll&lang=en_US"> (catalogue record)</a>](https://photos.smugmug.com/Exhibitions/Not-A-Day-exhibition/Ciphers-Gallery/i-LDFCq9Z/0/5d0a86ee/Ti/S-003-026-004-Ti.jpg)
![In this book on ciphers Porta, a popular Italian writer, describes Cardano’s most enduring invention, the Cardan grille. By placing the grille over paper and writing through the holes, then filling the spaces with meaningless or misleading text, the writer could hide the fact that a secret message even existed, a method called steganography.<br><br>
These leaves also contain the materials to construct the most famous piece of espionage equipment from the Renaissance – the cipher wheel. The cryptographer turned the inner disc at intervals to generate an unpredictable cipher, and the recipient, provided they knew the encoder’s 'key', used their identical cipher wheel to decipher the message. That both key and wheel were required to crack the code made it an extremely secure form of cryptography. On the innermost disc, shown here, the hand of God points to the truth.<br><br>
[One of two pages shown]
<br><br>
<b>Author:</b> Giambattista della Porta <br>
<b>Title:</b><i> De occultis literarum
</i> [On the concealment of letters] (Montbeliard, 1593)<br>
<b>Shelfmark:</b> S.3.26 <a href="http://idiscover.lib.cam.ac.uk/primo-explore/fulldisplay?docid=44CAM_ALMA21413388950003606&context=L&vid=44CAM_PROD&search_scope=SCOP_QUE&tab=cam_lib_coll&lang=en_US"> (catalogue record)</a>](https://photos.smugmug.com/Exhibitions/Not-A-Day-exhibition/Ciphers-Gallery/i-4bqvzv2/0/90dbf318/Ti/S-003-026-050-Ti.jpg)
![[One of two pages shown - the cipher wheel]
<br><br>
<b>Author:</b> Giambattista della Porta <br>
<b>Title:</b><i> De occultis literarum
</i> [On the concealment of letters] (Montbeliard, 1593)<br>
<b>Shelfmark:</b> S.3.26 <a href="http://idiscover.lib.cam.ac.uk/primo-explore/fulldisplay?docid=44CAM_ALMA21413388950003606&context=L&vid=44CAM_PROD&search_scope=SCOP_QUE&tab=cam_lib_coll&lang=en_US"> (catalogue record)</a>](https://photos.smugmug.com/Exhibitions/Not-A-Day-exhibition/Ciphers-Gallery/i-PzbBdds/0/af0c2c50/Ti/S-003-026-051-Ti.jpg)
![Girolamo Cardano, born in Pavia in 1501, was an Italian physician, mathematician and astrologer. He is remembered for his frank memoir, written while under house arrest for heresy, and the offending work, <i>On subtlety</i>. In this chapter, along with methods to encode letters, write in invisible ink and send secret signals by fire, Cardano describes his system for recording large numbers as a single character. He wrongly attributes the system to Agrippa, but in fact these are Basingstoke ciphers, used by English Cistercian monks in the thirteenth century for marking pagination in manuscripts. Cardano’s method becomes unreliable once it enters five figures, but can be used to illustrate numbers into the billions. <br><br>
(One of two pages)
<br><br>
<b>Author:</b> Girolamo Cardano <br>
<b>Title:</b><i> De subtilitate libri XXI </i> [On subtlety] (Basel, 1582)<br>
<b>Shelfmark:</b> H.18.14 <a href="http://idiscover.lib.cam.ac.uk/primo-explore/fulldisplay?docid=44CAM_ALMA21392190740003606&context=L&vid=44CAM_PROD&search_scope=SCOP_QUE&tab=cam_lib_coll&lang=en_US"> (catalogue record)</a>](https://photos.smugmug.com/Exhibitions/Not-A-Day-exhibition/Ciphers-Gallery/i-3mrGtkV/0/ac13a1db/Ti/H-018-014-006-Ti.jpg)