cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

, a scytale (; also transliterated skytale, grc, σκυτάλη ''skutálē'' "baton,

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

", also ''skútalon'') is a

tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates ba ...

used to perform a

transposition cipher In cryptography, a transposition cipher is a method of encryption which scrambles the positions of characters (''transposition'') without changing the characters themselves. Transposition ciphers reorder units of plaintext (typically characters or ...

, consisting of a cylinder with a strip of parchment wound around it on which is written a message. The

ancient Greeks Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...

, and the

Sparta Sparta ( Doric Greek: Σπάρτα, ''Spártā''; Attic Greek: Σπάρτη, ''Spártē'') was a prominent city-state in Laconia, in ancient Greece. In antiquity, the city-state was known as Lacedaemon (, ), while the name Sparta referre ...

ns in particular, are said to have used this cipher to communicate during

military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...

campaigns. The recipient uses a rod of the same

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

on which the parchment is wrapped to read the message. To cryptanalyse it is not difficult. Use a tapered cone. Wrap the strip around it. Somewhere plaintext will be visible. That is the diameter of the rods used.

Encrypting

Suppose the rod allows one to write four letters around in a circle and five letters down the side of it. The

plaintext In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. This usually refers to data that is transmitted or stored unencrypted. Overview With the advent of com ...

could be: "I am hurt very badly help". To encrypt, one simply writes across the leather:

_____________________________________________________________
       ,    ,    ,    ,    ,    ,   , 
       ,  I ,  a ,  m ,  h ,  u ,   , 
     __,  r ,  t ,  v ,  e ,  r , __, 
    ,   ,  y ,  b ,  a ,  d ,  l , 
    ,   ,  y ,  h ,  e ,  l ,  p , 
    ,   ,    ,    ,    ,    ,    , 
_____________________________________________________________

so the

ciphertext In cryptography, ciphertext or cyphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext ...

becomes, "Iryyatbhmvaehedlurlp" after unwinding.

Decrypting

To decrypt, all one must do is wrap the leather strip around the rod and read across. The ciphertext is: "Iryyatbhmvaehedlurlp" Every fifth letter will appear on the same line, so the plaintext (after re-insertion of spaces) becomes: "I am hurt very badly help".

History

From indirect evidence, the scytale was first mentioned by the Greek poet Archilochus, who lived in the 7th century BC. Other Greek and Roman writers during the following centuries also mentioned it, but it was not until

Apollonius of Rhodes Apollonius of Rhodes ( grc, Ἀπολλώνιος Ῥόδιος ''Apollṓnios Rhódios''; la, Apollonius Rhodius; fl. first half of 3rd century BC) was an ancient Greek author, best known for the ''Argonautica'', an epic poem about Jason and t ...

(middle of the 3rd century BC) that a clear indication of its use as a cryptographic device appeared. A description of how it operated is not known from before

Plutarch Plutarch (; grc-gre, Πλούταρχος, ''Ploútarchos''; ; – after AD 119) was a Greek Middle Platonist philosopher, historian, biographer, essayist, and priest at the Temple of Apollo in Delphi. He is known primarily for hi ...

(50–120 AD): Due to difficulties in reconciling the description of Plutarch with the earlier accounts, and circumstantial evidence such as the cryptographic weakness of the device, several authors have suggested that the scytale was used for conveying messages in

and that Plutarch's description is mythological.

Message authentication hypothesis

An alternative hypothesis is that the scytale was used for message authentication rather than encryption. Only if the sender wrote the message around a scytale of the same diameter as the receiver's would the receiver be able to read it. It would therefore be difficult for enemy spies to inject false messages into the communication between two commanders. Nonetheless, any person intercepting a scytale message, and having heard about the method, could with little difficulty find out the rod size needed (a kind of brute force attack); once knowing that, it would be easy to supplant the sender and forge new messages.

Encrypting

Decrypting

History

Message authentication hypothesis

See also

References

Further reading