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Encyclopedia of Cryptography and Security pp 465Cite as

Porta Encryption

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This particular encryption method works on an alphabet of \(N= 2\cdot \nu\) letters. A Porta encryption step (Giambattista della Porta, 1563) is a simple substitution (see substitutions and permutations) consisting of ν swaps (cycles of length 2). Typically, there are ν such swaps, each one designated by two key letters in a polyphonic way. A Porta encryption is self-reciprocal. For an example of a PORTA encryption see the section “autokey” in the entry key.

A Porta table for Z 20 (G.B.della Porta and M. Argenti/, 1589) is given by:

$$ {\fontsize{7.8}{10}{\selectfont{\begin{array}{@{}|cc@{}|@{}cccccccccc|@{}} \hline A&B& {\rm (a m)}& {\rm (b n)}& {\rm (c o)}& {\rm (d p)}& {\rm (e q)}& {\rm (f r)}& {\rm (g s)}& {\rm (h t)}& {\rm (i u)}& {\rm (l x)}\\ \hline C&D& {\rm (a x)}& {\rm (b m)}& {\rm (c n)}& {\rm (d o)}& {\rm (e p)}& {\rm (f q)}& {\rm (g r)}& {\rm (h s)}& {\rm (i t)}& {\rm (l u)}\\ \hline E&F& {\rm (a u)}& {\rm (b x)}& {\rm (c m)}& {\rm (d n)}& {\rm (e o)}& {\rm (f p)}& {\rm...

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References

  1. Bauer, F.L. (1997). “Decrypted secrets.” Methods and Maxims of Cryptology. Springer-Verlag, Berlin.

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Authors
  1. Friedrich L. Bauer
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Editors and Affiliations

  1. Eindhoven University of Technology, Eindhoven, The Netherlands

    Henk C. A. van Tilborg

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© 2005 International Federation for Information Processing

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Bauer, F.L. (2005). Porta Encryption. In: van Tilborg, H.C.A. (eds) Encyclopedia of Cryptography and Security. Springer, Boston, MA . https://doi.org/10.1007/0-387-23483-7_308

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