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Section 3.2 Variation on a Theme

Subsection 3.2.1 Biography of Heinrich Cornelius Agripa

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Subsection 3.2.2 Pigpen Cipher

In his treatise on cryptology [16, p. 275b (534)] Vigenère describes a cipher that he found in Agripa's De Occulta Philosophia [1, Vol. 3, p. CCLXXV (279)] in chapter 30 which discusses traditional ciphers used by cabals.

Vigenere's Pigpen Variant
Figure 3.2.1. Vigenere's Variant on the Pigpen Cipher
Agripa's Pigpen Variant
Figure 3.2.2. Agripa's Variant on the Pigpen Cipher

One may frame nine chambers by the intersection of four parallel lines intersectiong themselves at right angles as expressed in the figure:

Which being dissected into parts generates nine the particular figures:

from the nine chambers. Characterize each letter in a chamber by the notation of one point to show the first letter in the chamber; two for the second letter; three for the third letter; so that the characters of Michael may be written in seven characters:

Which may be written one after another drawn as three figures:

Which written one after another drawn as one figure, omitting the usual marks, gives the characters of Michael as:

[1, Vol. 3, CCLXXV (p.279)] [2, Vol.3, Chapter XXX]  1 

The translation is based, for the most part, on [2] with reference to the original text. The example was changed some in order to make the work more accessible.`

Comprehension Check:

  • If you hadn't seen the first step in how the name “Michael” was enciphered above, then how might you misinterpret the second enciphering?
  • Why in the final step do you think some of the symbols must be raised or lowered?
  • In the final step above Agripa eliminates all the marks, why would this cause confusion? That is, if you follow his directions which letters will be confused with one another?
  • In the translated grid the letters are placed into the grid right to left, this is also the case in Agripa's work Figure 3.2.2, try to find out why.

Use Agripa's cipher as translated above to encipher the quote: “Pigs are smarter than dogs, and both are smarter than Congress” - Elayne Boosler

Answer

Here are the first few words of the message:

Figure 3.2.4. Cipher Text:

Decipher the words enciphered here using Agripa's cipher as presented above.

Figure 3.2.6. Cipher Text:
Answer

Plaintext: “Pork 'n Beans”

The pigpen cipher as we use it today has evolved and standardized to use the key in Figure 3.2.7 which includes all twenty six letters of modern English. It has the advantages that it is quick to learn and it is easy to recreate the cipher key. Also, for each shape you never add more than a single dot so that there is less opportunity for confusion.

Modern Pigpen Cipher
Figure 3.2.7. Modern key for the Pigpen Cipher

Use the key in Figure 3.2.7 to decipher the message below.

Figure 3.2.9. Cipher Text
Answer

“I am fond of pigs. Dogs look up to us. Cats look down on us. Pigs treat us as equals.” ― Winston S. Churchill

Try to encipher the first few words of this next message using the modern variation on the pigpen cipher (Figure 3.2.7).

“Never wrestle with pigs. You both get dirty and the pig likes it.” ― George Bernard Shaw

Answer
Figure 3.2.11. Cipher Text

Reflection:

  • Do you think that the pigpen cipher offers as much security as the Vigenère cipher? Why or why not?
  • In how many ways can you encipher each character using the pigpen cipher? What type of cipher does that make this?
  • If you were confronted with a similar cipher which used symbols in place of letters how could you first rewrite your message so that you could then apply the cryptanalysis techniques we discussed previously?