Scytale Not As a Transposition Cipher

A scytale (or skytale) is usually described as a simple tool for transposition cipher (Wikipedia; David Kahn, The Codebreakers (1967) p. 82; etc.), which uses a baton and a strip of paper (or parchment or whatever). Historically, however, there were accounts incompatible with this understanding.

Table of Contents:

Two Explanations for Scytale

Historical Explanations of Scytale

Classic Sources of Scytale

Tentative Conclusion

Further Sources

Two Explanations for Scytale


Scytale as a Transposition Cipher

A scytale is usually described as a tool for enciphering by wrapping a strip around a baton and writing letters in the direction of the axis of the baton. When the strip is unwrapped, the sequence of the letters along the strip does not make sense but, when the strip is wrapped around a baton of the same thickness, the message can again be read axially. This is equivalent to writing letters in a grid vertically and picking up letters horizontally (or vice versa) to form a ciphertext. This is a form of a transposition cipher, whereby the letters of the plaintext are shuffled without being changed to different letters or symbols.

(By the way, this scheme is featured as Pythagora Cipher Baton (pitagora ango bo) (YouTube) in a Japanese TV program for kids called PythagoraSwitch (Wikipedia).)

(By the way, I have long thought one held the scytale vertically but I noticed most images on the Web depict it horizontally. So I corrected the above image to reflect it. Indeed, it may be more natural for Westerners to write the plaintext horizontally.)

Alternative Scytale

Some early modern sources describe a scytale differently. A strip is again wrapped around a baton but letters are written along where the edges of the strip meet (so that the center of the line of writing is over the edges). Thus, when the strip is unwound, only fragments of the letters can be seen on either side of the strip.

(By the way, a similar scheme was used in a Japanese TV drama Hard Nuts (2013) (Wikipedia). In this episode, the letters were broken to tiny stains on a string and presence of information was concealed (i.e., steganography).)

Historical Explanations of Scytale

Giovanni Battista Porta, De Occultis Literarum Notis (1593)

(Google)

Porta's classic work on cryptology (see another article) discusses scytale in Book 1, Chapter XII and points out its weakness in Chapter XIIII.

Testis est Gellius in libris noctium Atticarum Lacedemonas cum ad imperatores suos scriberent, ne literae interceptae occulta hostibus consilia indicarent, hoc scripti genus ex industria excogitasse, quamuis alii eius rei commentum ad Archimedem Syracusanum referant. Surculi duo teretes longitudo & latitudo esset, eorum alter imperatori ad bellum proficiscenti dabatur, alter domi penes magistratus diligenter servabatur, quoties itaque usus necessitas incidebat, pagina, quanta rei satis erat, surculo circumvoluta, ut rotundum volumen efficerer, & orae bene adiunctae in modum lori apte ligno cohaererent, ne rimae interponerentur, tum in chartam sic circumvolutam literae a summo capite per transversum ad imum in eo loro inscribebantur. Perscriptum inde loru surculo prolixum, &angustum eximebatur, & ad imperatorem dabatur, existimabant enim si in hostium manus illud forte interceptum incidisset, truncatas literas, syllabas, dictionesque, & eorum partes longe distractas intuentes scriptum nequaquam percepturos, nec spem frustrabatur eventus, quoties enim illud in hostes incidebat, nihil in loro scriptum poterant coniectari, sed velut incondite & frustra scriptum dimittebant, is vero, cui illud destinabatur, applicato loro, in eumque modum circumvoluta, quo antea fuerat, cum scriberetur, ita ut continuata scripti series sequeretur, nuncium agnoicebat. Huiusmodi scriptum [Scytala] Graece appellabant. In hunc modi scriptam epistolam Lisandro ad Hellespontu allatam Plutarchus author est....

The appendix of the 1593 edition cites some other medieval references (p.13-14) and reproduces an illustration from a work by a Brechtelus. This clearly illustrates scytale was not understood as a transposition cipher.


John Wilkins, Mercury (1641)

The first work known to me to have described the "writing over edges" interpretation is John Wilkins, Mercury (see another article) p.37-39. He discusses scytale in Chapter 5 for secret writing by means of materials, rather than in Chapter 6 for transposition ciphers.

The chief contrivance of secrecy by the paper, in use amongst the Ancients, was the Lacedemonian Scytale: The manner of which was thus: there were provided two round staves of an equall length and size: the Magistrates always retaining one of them at home, and the other being carried abroad by the Generall, at his going forth to warre. When there was any secret businesse to bee writ by it, their manner was to wrap a narrow thong of Parchment about one of these staves, by a serpentine revolution, so that the edges of it might meet close together: upon both which edges they inscribed their Epistle, whereas the Parchment being taken off, there appeared nothing but pieces of letters on the sides of it, which could not be joyned together into the right sense without the true Scytale. Thus is it briefly and fully described by Ausonius.
Vel Lacedemoniam Scytalen imitare libelli,
Segmina Pergamei, tereti, circumdata ligno.
Perpetuo inscribens versu, deinde solutus,
Non respondentes sparso dabit ordine formas.

You may read in Plutarch, how by this means, Pharnabaz did deceive Lysander.

In discussing a weakness of the scytale, Wilkins mentions "Exerc, 327" by Scaliger (Wikipedia), which appears to refer to Exotericarum exercitationum (a 1557 edition is at Gallica; a 1607 edition is at Google) but I could not locate the reference. The above quotation from Ausonius will be mentioned below.

John Falconer, Cryptomenysis Patefacta (1685)

Falconer (see another article) quotes Wilkins' explanation.

Georges Guillet de Guilletiere, Lacédémone ancienne et nouvelle (1676)

(Vol.2, p.524-526, Google)

Guillet de Guilletiere's expression "l'écriture estoit tronquée" seems to be different from transposition cipher, but "les mots sans liaison" (words without connection) may be interpreted both ways. (He also points out another interpretation that a scytale is merely a single baton cut into two equal parts along its length rather than a cipher device.)

C'estoient deux rouleaux de bois d'une longueur & d'une épaisseur égale, que le travail du tour avoit parfaitement arrondis. Les Ephores en conservoient un, & donnoient l'autre au General d'Armée qui marchoit contre l'Ennemy. Chaque fois que ces Souverains Magistrats lui vouloient envoyer des Ordres secrets, qui ne pussent estre déchiffrez en cas qu'on les interceptat, ils prenoient une bande de parchemin étroite & longue, qu'ils rouloient avec justesse autour de la Scytale, ou Rouleau qu'ils s'estoient reservez. En cet estat ils y écrivoient leurs intentions, qui paroissoient dans un sens parfait, tant que la bande de parchemin estoit appliquée sur le Rouleau; mais dés qu'on la développoit, l'écriture estoit tronquée, & les mots sans liaison. Il n'y avoit que le General seul, qui pût y trouver de la suite & du sens, en ajustant la bande sur le rouleau semblable, & la remettant dans la mesme assiete où les Ephores l'avoient mise. Il se trouve des Autheurs, qui disent que la Scytale n'estoit composée que d'un seul rouleau coupé en deux parties égales selon sa longueur, une pour les Ephores, & l'autre pour le General d'Armée.

A Google search for "Guilletiere scytale" returns many books citing this work. Even the Encyclopedia of Diderot and D'Alembert (see below) relies on this work.

Le Journal des Scavans de l'an M.DC.LXXVI. (1683) (p.183, Google)

Dictionnaire Universel Francois Et Latin, vol.2 (1743) (under CHIFFRE, Google)

Real, La science du gouvernement, vol.6 (1761) (p.414, Google)

Real, Die Staatskunst, vol.6 (1767) (p.569, Google)

Dizionario delle arti e de' mestieri vol.16 (1774) (p.176, Google)

Dictionnaire universel des sciences morale, économique, politique et diplomatique, ou bibliothèque de l'homme d'état et du citoyen vol.11 (1779) (under CHIFFRE, Google)

Franz Xavier von Moshamm, Europäisches Gesandschaftsrecht (1805) (p.421, Google)

Alphonse Costadau, Traité Historique et Critique des principaux signes dont nous nous servons pour manifester nos pensées (1717)

(Google)

La Scytale étoit un bâton ou rond, ou quarré, dont les Lacedemoniens se servoient pour écrire à leurs Correspondans des lettres secretes. Celui qui écrivoit tortilloit autour du bâton une corroye, ou laniere de parchemin, & sans user de chiffres, & sans transposer les lettres de l'Alphabet y écrivoit ce qu'il avoit à mander, & l'envoyoit au correspondant & celui-ci l'appliquant sur un autre bâton qu'il avoit de même grosseur, trouvoit les mots & les lignes en la même disposition qu'on les avoit écrits, au lieu qu'il n'auroit pû les lire s'il n'eût eu un bâton semblable & en grosseur & en figure à celui de l'autre qui lui écrivoit, attendu qu'alors ils n'auroit trouvé que des lettres ou confonduës, ou dissipées. Cependant cette invention est assès grossiere, quoique les Lacedemoniens en fissent un grand cas. Celle du Chassis est bien plus subtile, & si la correspondance est bien établie, une lettres est indechiffrable.

Diderot and d'Alembert, Encyclopédie (1751-1772)

(Volume 14, 1765, Wikisource)

The basic explanation appears to be taken from Guillet de Guilletiere.

SCYTALE ...
Il faut donc sçavoir que les Lacédémoniens, pour empêcher qu'on ne pût déchiffrer les ordres qu'ils envoyoient par écrit à leur général d'armée, imaginerent de faire deux rouleaux de bois, d'une longueur & d'une épaisseur égale, & que le travail du tour avoit parfaitement arrondie ; les Ephores en conservoient un, & donnoient l'autre au général d'armée, qui marchoit contre l'ennemi. Chaque fois que ces souverains magistrats lui vouloient envoyer des ordres secrets, qui ne pussent être déchiffrés en cas qu'on les interceptât, ils prenoient une bande de parchemin étroite & longue, qu'ils rouloient avec justesse autour de la scytale ou rouleau de bois. En cet état ils écrivoient sur la bande de parchemin leurs intentions, qui paroissoient dans un sens parfait tant que la bande de parchemin étoit appliquée sur le rouleau ; mais dès qu'on la developpoit, l'écriture étoit tronquée, & les mots sans liaison; il n'y avoit que le général seul qui pût y trouver de la suite & du sens, en ajustant la bande sur le rouleau semblable, & la remettant dans la même assiette où les éphores l'avoient mise.... (D.J.)

Similar descriptions are found under CHIFFRE (Wikisource, Google) in Volume 3, citing Guillet de la Guilletiere.

The entry DECHIFFRER (Wikisource, Google) explains how easily the scytale cipher could be solved, which provides some insight on how the scytale was understood by the author.

DECHIFFRER ...
J'observerai seulement que cette espece de chiffre ne devoit pas être fort difficile à deviner: car 1o. il étoit aisé de voir, en tâtonnant un peu, quelle étoit la ligne qui devoit se joindre par le sens à la ligne d'en-bas du papier: 2o. cette seconde ligne connue, tout le reste étoit aisé à trouver; car supposons que cette seconde ligne, suite immédiate de la première dans le sens, fût, par exemple, la cinquième, il n'y avoit qu'à aller de-là à la neuvième, à la treizième, à la dix-septième, &c. & ainsi de suite jusqu'au haut du papier, & on trouvoit toute la première ligne du rouleau. 3o. Ensuite on n'avoit qu'à reprendre la seconde ligne d'en-bas, puis la sixième, la dixième, la quatorzième, &c. & ainsi de suite, Tout cela est aisé à voir, en considérant qu'une ligne écrite sur le rouleau, devoit être formée par des lignes partielles également distantes les unes des autres....

From the reference to "equally distant", the transposition cipher is clearly intended. Further, the transposition is not letter by letter but several letters ("partial line") are written within the breadth of the strip. This is similar to the scheme proposed by Hulme in 1898. (For right-handed people, the winding of Hulme would be more natural than my drawing below, in which case the plaintext words should be picked from the bottom to the top, as explained in the encyclopaedia.)


Philip Thicknesse, A treatise on the art of decyphering (1772)

Thicknesse's treatment of scytale again follows that of Wilkins (p.18). The description of its deciphering also shows that the letters were to be written along the border of edges.

notwithstanding the seeming difficulty of reading a scrole, so writ, without the stave, there are many ways by which it might be made out, as Scaliger in a few words clearly demonstrates, for says he, only twist the paper, or parchment, so that both pieces of the first divided letter may be joined, and that will give the true circumference of the scytale to frame another by; but I wonder Scaliger did not think of a much more ready method, and that is, by cutting the scrole quite through the middle between the half letters, and then, by applying the two broken edges of the letters together, on a table, the letters will appear perfect, and consequently the reading be exposed.

Jean Lanteires, Bibliothèque du père de famille ou cours complet d'éducation (1795)

(Google)

In a section "De l'écriture", a footnote about cryptography mentions scytale with similar wording to the Encyclopédie but also uses words not used in the latter such as "suivi" or "suite".

Lorsque ces Magistrats voulaient lui envoyer des ordres secrets, ils prenaient une bande de parchemin étroite & longue, qu'ils roulaient exactement autour de la Scytale qu'il s'était reservée: ils écrivaient alors dessus leurs intentions; & ce qu'ils avaient écrit formait un sens parfait & suivi, tant que la bande de parchemin était appliquée sur le rouleau; mais dès qu'on le développait, l'écriture était tronquée & les mots sans liaison, & il n y avait que le Général qui put en trouver la suite & le sens, en ajustant la bande sur la Scytale ou rouleau semblable qu il avait.

The Wonders of the Little World, Or, A General History of Man ... (1806)

(Google) p.474

Chapter XLIV "Of the secret Ways of Dispatch, and the Delivery of Messages by Letters, Cyphers, and other Ways" (p.473-475) describes ancient means of secret correspondence. The sources for the section 5. for scytale are: (i) A. Gell. Noct. Attic. l.17. c.9. p.458 [see The Attic Nights below]; (ii) Erasm. Adag. p.442. [Erasmus, Adagia, 1101 II-II-1 Tristis Scytale, annotated text, Google]; (iii) Zuing. [Zuinglium, i.e., Zwingli?] Theat. vol.3.l.4 p.156; (iv) Plut. in Lysandr. p.144 [see below]; (v) Pet. Gregor. de Repub. l.16.c.4. p.667. Thus, this work is independent of the "writing over edges" interpretation of Wilkins, Falconer, and Thicknesse.

The ancient Lacedaemonians, when they had a purpose to dissemble and conceal their letters, which they sent to their generals abroad, that the contents of them might not be understood, though they should be intercepted by the enemy, they took this course: they chose two round sticks, of the same thickness and length, wrought and planed after the same manner. One of these was given to their general when he was about to march, the other was kept at home by the magistrates. When occasion of secrecy was, they wound about this stick a long scroll, and narrow, only once about, and in such manner as that the sides of each round should lie close together; then wrote they their letters upon the transverse junctures of the scroll, from the top to the bottom. This scroll they took off from the stick, and sent it to the general, who knew well how to fix it to that stick he kept by him; the unrolling of it did disjoin the letters, confound and intermix them in such a manner, that although the scroll was taken by the enemy, they knew not what to make of it; if it passed safe, their own general could read it at pleasure. This kind of letter the Lacedemonians called Scytale.

While the expression "upon the transverse junctures of the scroll, from the top to the bottom" sounds like "writing over edges", the subsequent expression "intermix them [letters]" seems to indicate a transposition cipher. (The reference "from the top to the bottom" may indicate the baton is to be held vertically.)

William Blair, "Cipher", Rees' Cyclopaedia (1807)

Blair (see another article) describes deciphering methods for a scytale by Falconer (after Scaliger) and Thicknesse.

Johann Ludwig Klüber, Kryptographik. Lehrbuch der Geheimschreibekunst (Chiffrir- und Dechiffrirkunst) in Staats- und Privatgeschäften (1809)

Lacedämonier bedienten sich zu dem Geheimschreiben, welche die Regierung ihren Feldherren sendete, der Scytalae. Man fertigte zwei runde hölzerne Stäbe vom gleicher Länge und Dicke. Den einen verwahrte die Regierung, den andern der Feldherr. Wellte man diesem eine geheime Ordre senden, so wickelte man einen langen und schmalen Pergament Riemen mit Vorsicht um den Stab, und schrieb dann da, Nöthige auf die Extremitäten des Riemens, das wo solche einander berührten, so dass die Buchstaben zur Hälfte auf dem einen, zur Hälfte auf dem andern, an jenen anstossenden, Rande des Riemens standen.
Diesen Riemen, nachdem er von dem Stabe losgewickelt war, und so nur getrennte und unzusammenhängende Spuren von Schrift darauf wahrzunehmen waren, sendete man dem Feldherrn. Dieser wickelte solchen, bei dem Dechiffrieren, nach der Abrede über seinen Stab. Sobald die Extremitäten überall gehörig an einander passten, rückten die getrennten Theile der Buchstaben zusammen, und die Geheimschrift konnte gelesen werden.

This German author clearly indicates writing over edges with half of the letters on one strip and the other half on an adjacent strip.

Dictionnaire étymologique des mots français dérivés du grec (1809)

(Google, Google) p.323

SCYTALE ...
Les Lacédémoniens appeloient scytale, une bande de parchemin qui se tortilloit autour d'un rouleau, et sur laquelle on écri voit des lettres secrètes. Celui à qui l'on écrivoit, avoit un autre rouleau égal et correspondant, autour duquel il appliquoit cette bande; et par ce moyen, il trouvoit les lignes et les mots dans leur ordre naturel.

Words such as "mots" (words) and "ordre" (order) seem to indicate that the author considered the scytale as a transposition cipher.

"De la Cryptographie", Le magasin pittoresque, Vol. 6 or 5 (1837)

(Google, Google) p.43

While English sources tend to adopt "writing over edges" and French sources "transposition", the "writing over edges" interpretation is also seen in a French work.

La scytale était un bâton rond ou carré, dont le diamètre était environ de trois pouces et la longueur d'un pied et demi. On roulait en spirale autour de ce bâton une bande de parchemin large de deux pouces, en ayant soin d'en faire toucher partout les bords. La bande ainsi roulée, on l'arrêtait à ses deux extrémités avec de la cire, et l'on marquait d'un signe le commencement; on écrivait ensuite en spirale précisément à tous les endroits où les bandes se touchaient. Il en résultait que lorsque le parchemin était déroulé, la plupart des lettres se trouvaient coupées, sans qu'il fût possible de les rassembler, à moins d'avoir un bâton entièrement semblable.

Edgar Allan Poe, "Cryptography" (a.k.a. "A Few Words on Secret Writing") (1841)

The scytala were two wooden cylinders, precisely similar in all respects. The general of an army, in going upon any expedition, received from the ephori one of these cylinders, while the other remained in their possession. If either party had occasion to communicate with the other, a narrow strip of parchment was so wrapped around the scytala that the edges of the skin fitted accurately each to each. The writing was then inscribed longitudinally, and the epistle unrolled and dispatched. If, by mischance, the messenger was intercepted, the letter proved unintelligible to his captors. If he reached his destination safely, however, the party addressed had only to involve the second cylinder in the strip to decipher the inscription.

Although Poe is known to have used Blair's article, the description of its deciphering escaped his "cognizance" and Poe describes his own method for deciphering.

The strip of skin being intercepted, let there be prepared a cone of great length comparatively -- say six feet long -- and whose circumference at base shall at least equal the length of the strip. Let this latter be rolled upon the cone near the base, edge to edge, as above described; then, still keeping edge to edge, and maintaining the parchment close upon the cone, let it be gradually slipped towards the apex. In this process, some of those words, syllables, or letters, whose connection is intended, will be sure to come together at that point of the cone where its diameter equals that of the scytala upon which the cipher was written. And as, in passing up the cone to its apex, all possible diameters are passed over, there is no chance of a failure. The circumference of the scytala being thus ascertained, a similar one can be made, and the cipher applied to it.

Poe appears to have interpreted scytale to be a transposition cipher.

Paul Lacroix, La cryptographie, ou, L'art d'écrire en chiffres: les secrets de nos pères recueillis par le bibliophile Jacob (1858)

(Google p.6-10)

After quoting Plutarch and Ausonius (see below), it is explained how easily the cipher could be solved, which is clearly taken from the entry DECHIFFRER of Encyclopédie of Diderot and d'Alembert (see above).

Encyclopédie du dix-neuvième siècle, répertoire universel des sciences, des lettres et des arts (1846, 1852)

(Google, Google)

POLYGRAPHIE
... Les Grecs ignorènt pendant longtemps cette science et n'employèrent d'abord, pour le secret de leurs correspondences, que la scytale lacédémonienne, consistant en deux cylindres de bois entièrement pareils, et dont chacun restait entre les mains de l'un des correspondants. Lorsque l'on voulait écrire, on tortillait autour du rouleau une scytale ou lanière de parchemin fort étroite, sur laquelle étaient tracées des phrases ou des mots ne formant par eux-mêmes aucun sens complet, mais qui, mis en rapport avec les inscriptions communes aux rouleaux, en recevaient une signification claire et précise.

Expressions like "words" or "no sense" seem to indicate the author considers the scytale as a transposition cipher.

Ch. de Bussy, Dictionnaire universel d'éducation (1866)

(Google) p.207

The substantive part is taken from Encyclopédie du dix-neuvième siècle (1846, 1852) above.

Pendant longtemps les Grecs se servaient à cet effet de la scytale lacédémonienne, qui consistait en deux cylindres de bois pareils, et dont chacun restait entre les mains de l'un des correspondants. Lorsque l'on voulait écrire, on tortillait autour du rouleau une scytale ou lanière de parchemin fort étroite, sur laquelle étaient tracées des phrases ou des mots ne formant par eux-mêmes aucun sens complet, mais qui, mis en rapport avec les inscriptions communes aux rouleaux, en recevaient une signification claire et précise.

Encyclopaedia Britannica (1878)

(Google)

CRYPTOGRAPHY
...
The Lacedaemonians, according to Plutarch, had a method which has been called the scytale, from the staff (σκυταλη) employed in constructing and deciphering the message. When the Spartan ephors wished to forward their orders to their commanders abroad, they wound slantwise a narrow strip of parchment upon the σκυταλη so that the edges met close together, and the message was then added in such a way that the centre of the line of writing was on the edge of the parchment. When unwound, the scroll consisted of broken letters; and in that condition it was despatched to its destination, the general to whose hands it came deciphering it by means of a σκυταλη exactly corresponding to that used by the ephors.

This clearly indicates "writing over edges".

Edward Samuel Farrow, Farrow's Military Encyclopedia: A Dictionary of Military Knowledge (1885)

(Google) p.435

CRYPTOGRAPHY
...
The Lacedaemonians, according to Plutarch, had a method which has been called the scytale, from the staff employed in constructing and deciphering the message. When the Spartan Ephors wished to forward their orders to their Commander abroad, they wound slantwise a narrow slip of parchment upon the staff so that the edges met close together, and the message was then added in such a way that the center of the line of writing was on the edge of parchment. When unwound, the scroll consisted of broken letters; and in that condition it was dispatched to its destination; the General to whose hands it came deciphering it by means of a staff exactly corresponding to that used by the Ephors.

This appears to be a minor adaptation of Britannica's article and clearly indicates "writing over edges".

William R. Plum, The Military Telegraph During the Civil War in the United States, vol.1 (1882)

When the general of the army ventured into the enemy's country, or was cut off in his own, he communicated with the Spartan Ephors by the use of a staff called a scytale, an exact duplicate of which was possessed by the Ephors. The party desiring to write, first wound a slip of parchment around the staff, and then wrote his message lengthwise with the stick. After which, when it was unrolled, only unmeaning letters wholly unconnected with one another appeared; but the receiver rewound the ribbon on his scytale, and all was plain. (p.40)

"Les écritures chiffrées et leurs applications", Revue scientifique (Revue rose) (1887)

(Google, Google) p.290

Les Grecs employaient la scylale pour correspondre secrètement. C'était un bâton rond sur lequel on enroulait en hélice une bande de parchemin; on écrivait, transversalement, le long de ce bâton, la dépêche à transmettre et on déroulait le parchemin qu'on envoyait au correspondant; celui-ci, muni d'un bâton de semblable diamètre, enroulait le parchemin sans laisser d'espace et lisait la communication sans difficulté. Le déchiffrement de la scytale, est-il besoin de le dire, ne présentait qu'un faible obstacle aux curieux. On a proposé d'employer un procédé analogue dans lequel un fil remplaçait le parchemin, mais ce système est rien moins que pratique.

This clearly indicates a transposition cipher.

Rosalie Kaufman (ed), Our Young Folk's Plutarch (1890)

(Google) This adaptation of Plutarch "in a condensed, simple form" adopts "writing over edges".

When the Ephors wanted to send a secret communication, they took a long, narrow strip of parchment and rolled it from end to end on the scytale like a bandage; they then wrote upon the parchment following the direction of the wrapping, took it off, folded it, and sent it to the possessor of the corresponding scytale, who could read the message only after the parchment was bound as it had been when it was written upon.

W. W. Rouse Ball, Mathematical Recreations and Essays (1892 1st ed.,1914 6th ed.)

(Internet Archive, p.402)

... An example is a message written across the edges of a strip of paper wrapped spiral-wise round a stick called a scytale. When the paper is unwound and taken off the stick the letters appear broken, and may seem to consist of arbitrary signs, but by wrapping the paper round a similar stick the message can be again read.

William Shepard Walsh, Handy-book of Literary Curiosities (1892)

(Google) This uses the explanation of Britannica (1878) or Farrow's Military Encyclopedia (1885).

Carmona, Tratado de Criptografia con Aplicacion especial al Ejercito (1894)

This describes scytale under transposition cipher (p.36). The author appears to have been aware of a (theoretical) possibility of transposition by letters.

Entre los aparatos de transposición más antiguos (y más sencillos por cierto), se encuentra éste, que no es otra cosa que un cilindro de madera, marfil ú otra materia cualquiera, de longitud y grueso arbitrarios, al cual se enrolla una tira de papel (pergamino en aquellos tiempos), más ó menos estrecha, hasta quedar totalmente cubierto por ella. Después se escriben naturalmente sobre el papel, en el sentido del eje del cilindro, todos los renglones que sean necesarios, y concluído, se desenrolla la tira y envía al destinatario, quien se vale para leerla de otro cilindro de iguales dimensiones que al efecto tiene.
Como se comprenderá, el aparato es de lo más inocente que cabe, y únicamente lo citamos por la importancia histórica que pueda tener.
Fué empleado con frecuencia por los ejércitos griegos en campaña.
La transposición que con él se verifica es de palabras enteras, ó trozos de palabras, no de letras.

Edward Hulme, Cryptography, or, The History, Principles, and Practice of Cypher-Writing [1898]

(Internet Archive)

Although the scytale is not named, the author describes in some detail (p.47-51) the scheme ascribed (incorrectly) by Porta to Archimedes and also described by Plutarch and other ancient authors. After explaining the "writing over edges" scheme and how easily it could be detected, he observes: "A much better way of working this spiral paper method is to write the message, not along the edges, but right across the strips themselves." Although his specimen seems too revealing (the plaintext is "Get another roller the same size, or you will not be able to read this communication."), it is remarkable that he pointed out that the device considered to be used in one way could also be used in another way to provide more security.


"Secret Correspondence", The Illustrated American, Vol. 8, No. 89 (1891)

(Google)p.536

This uses the description of Farrow's Military Encyclopedia (1885).

The scytale of the Lacedaemonians, so called from the staff employed in constructing and deciphering the message, seems to have been the earliest approach to our modern cipher despatches. When the Spartan ephors wished to forward their orders to their commanders abroad, they wound slantwise a narrow strip of parchment upon the scytale so that the edges met close together, and the message was then added in such a way that the centre of the line of writing was on the edges of the parchment. When unwound, the scroll consisted of broken letters, and in that condition it was despatched to its destination, the general to whose hands it came deciphering it by means of a scytale exactly corresponding to that used by the ephors.

Étienne Bazeries, Les Chiffres Secrets Dévoilés (1901)

The great decipherer of the age says (p.7) the scytale is described by a bibliophile Jacob's les Secrets de nos Pères (which appears to be the work of Paul Lacroix (1858) above) and discusses it as a transposition cipher. While his source refers to transposition by partial lines, Bazeries must have seen that more than one letters in a breadth of the strip would give a clue to a decipherer, as pointed out by Mercure de France (1919) below. Bazeries' example of enciphering is transposition by letters, which is how the scytale is understood to work today.

F. Delastelle, Traité élémentaire de cryptographie: mathematiques appliquées (1902)

This classifies the scytale as an apparatus of transposition.

APPAREILS CRYPTOGRAPHIQUES
Les appareils cryptographiques, connus encore sous le nom de cryplographes, sont fort nombreux. La première classe renferme les appareils de transposition, tels que la scytale des Lacédémoniens, qui ...

The new international encyclopedia (1907)

A narrow strip of parchment was first wound spirally upon the staff, its edges just meeting, and the message was then written along the line of jointure. When it was unsound, the broken letters could afterwards be read only by rolling the partchment upon a duplicate staff in possession of the genera to whom it was sent.

Mercure de France (sér. moderne) Vol. 132 (1919)

This advises writing only one letter in the breadth of the strip, i.e., transposition by letters (not by partial lines as in Diderot and d'Alembert) for the purpose of security.

p.322
... ensuite son message dans le sens de la longueur du bâton, en ayant soin de n'écrire qu'une lettre à la fois sur chaque révolution de la bande du papyrus. Il expédiait le ruban qui, dérouleé, ne présentait qu'une suite de lettres sans signification apparente. Le destinataire tortillait lui aussi la lanièr sur sa scytale et lisait aisément la lettre de son correspondant... si les deux cylindres étaient bien de ....

André Langie, Cryptography (English translation, 1922, of a 1918 work De la Cryptographie)

This describes as a transposition cipher (p.14, p.40).

The scytale was a cylindrical rod round which the sender of the secret message rolled a long band of papyrus in a spiral, after the fashion of the emblems which cover reed-pipes. On the wrapper thus formed he traced the words lengthwise along the rod, taking care to write only one letter at a time on each fold of the ribbon of papyrus. Once unrolled, this showed nothing but a meaningless succession of separate letters. The recipient rolled the band round a rod of the same length and diameter as that of the sender. The slightest difference in the diameter of the two rods made the reading of the message practically impossible.

St. Nicholas ... for Boys and Girls, Vol. 50, No. 2 (1923)

Assuming the scytale is held horizontally, "crosswise" seems to refer to transposition.

Well, those chaps used to wind a strip of parchment, or something, around a little rod they called a scytale, and write on it crosswise. When it was unrolled, no one, without the same size scytale, could read it. Now -- this strip of ours exactly fits around my scout staff! Mr. Sammis must have made it that way on purpose. Some fine work, eh?

Lectures pour tous: revue universelle et populaire illustrée (1936)

Les Grecs inventèrent le premier système connu de <<transposition>>. Quand un général partait en expédition, la Cité lui confiait un bâton rond, la scytale, dont elle avait l'exacte réplique. Pour rédiger un message, la scytale était enveloppée ...

Edogawa Ranpo, "Ango Kiho no Shurui" (Kinds of Cryptography) (1925, 1929, 1953)

Edogawa Ranpo (Wikipedia), a Japanese mystery writer, admired Edgar Allan Poe so much that he created the pseudonym "Edogawa Ranpo" to sound like a Japanized form of "Edgar Allan Poe". However, apparently, he did not follow Poe's interpretation of the scytale above (which admittedly was not explicitly stated). In this classification of cryptographic schemes, the scytale is classified under "(A) split tally", separate from either (D) transposition cipher or (E) substitution cipher. This seems to indicate "writing over edges".

When Nagata Junko, who had wide knowledge in cryptography, proposed a revision of Edogawa's classification in 1986, the scytale was already widely believed to be a tool for transposition cipher and he abandoned Edogawa's classification "(A) split tally" (Ango to Suiri Shosetsu (Cryptography and Detective Stories) p.30, 215).

Lillian de la Torre, "The Stolen Christmas Box" (1946)

This short story by Lillian de la Torre (Wikipedia) is one of the series featuring Samuel Johnson as a detective and tells an incident in the Thrales (Wikipedia). It appeared in Ellery Queen's Mystery Magazine in 1946 (Unz.org).

(The following includes a spoiler.) The story is set in 1774 and refers to a recent book on cryptography, which is considered to be Thicknesse' A treatise on the art of decyphering (1772) mentioned above. In addition to the "writing over edges" interpretation of scytale, an interesting cipher by writing an English sentence with similar sounding French words is also described by Thicknesse (p.91). However, the author did not employ Thicknesse's quick solution for the "writing over edges" scytale by "cutting the scrole quite through the middle between the half letters, and then, by applying the two broken edges of the letters together, on a table."

Interestingly, this story provides an example of the cipher obtained by the "writing over edges" scytale, which looks like oghams.


Classic Sources of Scytale

Plutarch, The Parallel Lives

(Wikipedia; Greek editions have been published under the title Plutarchi vitae parallelae, for which see, e.g., Wikisource (in German); the relevant description will be found on p.403 of Vol. II)

Plutarch's The Parallel Lives translated by Bernadotte Perrin (Loeb Classical Library edition, Wikipedia) has the following description under the Life of Lysander.

The dispatch-scroll is of the following character. When the ephors send out an admiral or a general, they make two round pieces of wood exactly alike in length and thickness, so that each corresponds to the other in its dimensions, and keep one themselves, while they give the other to their envoy. These pieces of wood they call scytalae. Whenever, then, they wish to send some secret and important message, they make a scroll of parchment long and narrow, like a leathern strap, and wind it round their scytale, leaving no vacant space thereon, but covering its surface all round with the parchment. After doing this, they write what they wish on the parchment, just as it lies wrapped about the scytale; and when they have written their message, they take the parchment off, and send it, without the piece of wood, to the commander. He, when he has received it, cannot otherwise get any meaning of it, -- since the letters have no connection, but are disarranged, -- unless he takes his own scytale and winds the strip of parchment about it, so that, when its spiral course is restored perfectly, and that which follows is joined to that which precedes, he reads around the staff, and so discovers the continuity of the message. And the parchment, like the staff, is called scytale, as the thing measured bears the name of the measure.

The expressions "the letters have no connection, but are disarranged" and "discovers the continuity of the message" seem to suggest a transposition cipher but the "writing over edges" interpretation may also be possible, whereas the subsequent expression "reads around the staff" may be interpreted as "writing over edges" more naturally.

The following is a translation by Dryden. While it also has "view round the outside", this version seems to refer to a transposition cipher.

... When they have done this, they write what they please on the scroll, as it is wrapped about the staff; and when they have written, they take off the scroll, and send it to the general without the wood. He, when he has received it, can read nothing of the writing, because the words and letters are not connected, but all broken up; but taking his own staff, he winds the slip of the scroll about it, so that this folding, restoring all the parts into the same order that they were in before, and putting what comes first into connection with what follows, brings the whole consecutive contents to view round the outside.

The following is a translation by Aubrey Stewart. This version is not very clear.

When this has been done they write upon the paper while it is upon the stick, and after writing they unwind the paper and send it to the general without the stick. When he receives it, it is entirely illegible, as the letters have no connection, but he winds it round the stick in his possession so that the folds correspond to one another, and then the whole message can be read.

The nature of transposition cipher is clear in the French translation (by Amyot (1801)) (Google, Google, Google, Google).

Cette scytale est une telle chose: quand les éphores envoient à la guerre un général ou un admiral, ilz font accoustrer deux petits bâtons ronds et les font entièrement égaler en grosseur et en grandeur; desquelz deux bastons ilz en retiennent l'un par devers eulx et donnent l'autre à celuy qu'ilz envoyent. Ilz appellent ces deux petits bastons scytales, et, quand ilz veulent faire secrètement entendre quelque chose de conséquence à leurs capitaines, ilz prennent un bandeau de parchemin long et estroit comme une courroye, qu'ilz entortillent à l'entour de leur baston rond, sans laisser rien d'espace vuide entre les bords du bandeau; puis quand ilz sont ainsi bien joints, alors ilz escrivent sur le parchemin ainsi enrollé ce qu'ils veulent, et, quand ilz ont achevé d'escrire, ilz desveloppent le parchemin et l'envoyent à leur capitaine, lequel n'y sçauroit aultrement rien lire ny cognoistre, parce que les lettres n'ont point de suitte ny de liaison continuée, mais sont escartées l'une ça, l'autre là, jusqu'à ce que, prenant le petit rouleau de bois qu'on luy a baillé à son partement, il estend la courroye de parchemin qu'il a reçue tout à l'entour, tellement que le tour et le ply du parchemin venant à se retrouver en la mesme couche qu'il avoit esté plié premièrement, les lettres aussi viennent à se rencontrer en la suitte continuée qu'elles doivent estre. Ce petit rouleau de parchemin s'appelle aussi bien scytale comme le rouleau de bois, ne plus ne moins que nous voyons ailleurs ordinairement que la chose mesurée s'appelle du mesme nom que fait celle qui mesure.

A German translation by Kaltwasser is found on Google (p.321).

Dieser konnte den erhaltenen Brief, der ohne Zusammenhang und ganz aus einander gerissen war, nicht anders lesen, als wenn er den Papierschnitt um seinen Stab herumwand, wodurch die Windung wieder in die gehörige Ordnung kam, das zweyte sich an das erste anschloß, und das Auge nun um den Stab herum den Zusammenhang finden konnte.

A Japanese translation by Kono Yoichi (mainly based on a Teubner edition edited by Cl. Lindkog-K.Ziegler (1914-1935)) have "letters are separated without connection" and "inspect around the baton to rediscover phrases in continuity".

……将軍はそれを受取つても,文字が連絡なくばらばらになつてゐるために,そのままでは読むことができないが,手許にあるスキュタレーを取つてその周りにパピュロスの片を巻附け,その螺旋が元のと同じ位置を取つて前のに次のが合ふやうにしてから,眼で棒の周りを辿つて続いてゐる文句を再び見出す.……
河野与一訳『プルターク英雄伝6』岩波文庫(1954)

Another translation by Tsurumi Yusuke is based on Dreyden's English version and provides no more information.

受け取った人は,文字が支離滅裂で,つながっていないから判断できないが,例の木を取り出して,細長い羊皮紙を巻きつければ,書かれたときと同一の状態に復帰するので,前後,相連続して,文書の内容全部が,木の表面に示されるのである.
鶴見祐輔訳『プルターク英雄伝4』潮文庫(1971, 1984)

A new scholarly translation by Yaginuma Shigetake (Wikipedia (in Japanese)) postumously published in 2011 from the Greek original (using a Teubner edition by Ziegler) is interesting in that it clearly indicates "writing over edges" by an expression "not forming letters".

指揮官がそれを受け取ったとき,パピルス面に見えるのは,ばらばらになっていて,字の体をなさないものであるゆえ,そのままではまったく読めない.しかし自分が持たされたスキュタレに,重なり目がきちんと合うように注意しながらパピルスを巻きつけ,スキュタレを回しながら句をたどって,伝えられた文言を読み取る.
柳沼重剛訳『プルタルコス英雄伝3』(2011)

Although many translations are consistent with the widely accepted "transposition cipher" interpretation, it must be born in mind that translations may reflect the translators' interpretation when the original is not very clear. It seems significant that a new sholarly translation in Japanese by Yaginuma clearly indicates "writing over edges".


The Attic Nights of Aulus Gellius

(Google) A translation (1795) of Noctes Atticae by Aulus Gellius (Wikipedia), a work from the second century.

The ancient Lacedaemonians, when they wanted to conceal and involve in mystery the public dispatches sent to their generals, lest, if intercepted, their councils might be known to the enemy, wrote their letters in this manner: -- there were two thin oblong twigs, cut of an equal length, and trimmed so as to resemble each other: one was given to the general when he went with the army, another the magistrates kept at home under their authority and seal; when they wished to carry on a private correspondence, they bound a piece of leather of moderate thickness and sufficient length round the twig, in a regular and simple manner, so that the ends of the leather which was bound round the twig met and were joined; within this leather they wrote letters transversly, the lines running from the bottom to the top. This leathern tablet, with its letters thus inscribed, rolled round the twig they sent to the general who was aware of the device, but the unrolling of the tablet rendered the letters imperfect and mutilated, and divided the parts and heads of them, by which means, if the tablet fell into the hands of the enemy, they could collect nothing from it; but when he to whom it was addressed received it, applying the fellow twig in his possession to the end of the tablet, according to previous directions, he bound it round, and thus the letters uniting by means of the same impression of the twig, were made perfect, and rendered the letter whole, undamaged, and easy to be read. This kind of epistle the Lacedaemonians called scytale.

Referring to the French or Latin text below, words such as "junctions" or "edges", omitted around "transversely" of the English translation, tempt one to consider it refers to "writing over edges" but this part may also be interpreted as "going across joined edges in longitudinal (or axial) lines." Still, the words such as "morceaux" in the French text suggests the "writing over edges" scheme. The reference "from the bottom to the top" (which seems to be a translation error for "from the top to the bottom" according to the French version) may indicate the baton is to be held vertically.

Ils inscrivaient ensuite sur cette lanière la lettre en chevauchant les bords joints sur des lignes qui partaient du haut jusque en bas.
Une fois la lettre écrite ainsi, ils déroulaient du bâton la lanière pour l'envoyer au général qui était au courant de cette invention. Or la lanière une fois détachée, les lettres devenaient morcelées et mutilées, morceaux et contours dispersés dans les directions les plus opposées; c'est pourquoi si cette lanière tombait aux mains des ennemis, ils ne pouvaient rien tirer de cet écrit. (Collard (2004))

The Latin text is as follows.

Litteras deinde in eo loro per transuersas iuncturarum oras uersibus a summo ad imum proficiscentibus inscibebant.... Id lorum litteris commenti istius conscio mittebant; resolutio autem lori litteras truncas atque mutilas reddebat membraque earum et apices in partis diuersissimas spargebat; propterea, si id lorum in manus hostium inciderat, nihil quicquam coniectari ex eo scripto quibat. (Collard (2004), Google)

Ausonius' Letter to Paulinus

The lines in Latin quoted by Wilkins (above) and others are translated as follows (Ausonius, with an English translation, Internet Archive p.110-113). The writer Ausonius is a Roman poet in the 4th century (Wikipedia). He is the last to describe the scytale as a practical scheme, after which the scytale is mentioned only in lexicons (Collard (2004)).

Or imitate the Spartan scytale, writing on strips of parchment wound about a rounded stick in continuous lines, which, afterwards unrolled, will show characters incoherent because sequence is lost, until they are rolled again about just such another stick.

A French translation in Collard (2004) is as follows.

Ou bien imite la scytale lacédémonienne, en écrivant en ligne continue sur des segments d'un parchemin de Pergame disposé autour d'un bâton arrondi, parchemin qui une fois déroulé donnera des caractères ne répondant à rien, en ordre dispersé, jusqu'à ce qu'il soit enroulé autour d'une surface circulaire d'un bois semblable.

The Latin text is repeated for reference.

Vel Lacedemoniam Scytalen imitare libelli, Segmina Pergamei, tereti, circumdata ligno. Perpetuo inscribens versu, deinde solutus, Non respondentes sparso dabit ordine formas.

Ancient Annotation of Thucydides

Plato uses the word scytale towards the end of Theaetetus (Wikipedia). According to Tanaka Michitaro, translator of a Japanese edition (Puraton Zenshu 2: Cratylus, Theaetetus, p.401), an ancient annotation of Thucydides' History Vol. 1 (131-1) explains "scytale" as a cryptologic device, which explanation is consistent with a transposition cipher. But the translator says Plato's reference in Theaetetus does not appear to mean such a cryptologic device.

……革紙……をこの棒の上から斜めに巻きつけて,徐々に下の方まで巻いて来たところで,この棒の上から下へ向かって縦に幾段かの層をなしている革紙の上へ文字を書き下す.そして書き終った時にこれを棒から離して革紙だけを使者に持たせて軍司令官のところへ遣わすのである.途中他の者がこの革紙を見てもでたらめに文字が書いてあるばかりで,意味を知ることはできないわけである.……ただし,ここではこのような事柄は別に考えられていないようである.
水地宗明,田中美知太郎(訳)『プラトン全集2 クラテュロス,テアイテトス』岩波書店(1974) p.401 注1

An annotation to one French edition (1852) (Google p.239) explains Plato's expression by referring to the cryptologic device, though it is not clear whether transposition or "writing over edges" was intended.

Tentative Conclusion

(This section has been thoroughly rewritten in September 2015.)

Trend of Historical Descriptions

Ever since Wilkins (1641), many English sources adopted the "writing over edges" interpretation, even after Hulme [1898] proposed that the same device might be used differently (transposition by partial lines). While French sources may have referred to transposition, the references were not very clear. Possibly, "transposition by partial lines" may have been intended, as is clear in Encyclopédie of Diderot and d'Alembert (1751-1772). To the best of my knowledge, before Bazeries (1901), scytale as a tool for transposition letter by letter was barely implied by reference to "letters" in Amyot's translation (1801) of Plutarch or Plum (1882).

Scytale as a Tool for Breaking Lines into Fragments

In September 2015, the present author found a reference by Klüber (1809) to an illustration on p.14 in the appendix of Porta's classic work (1593). This appears to show a reasonable interpretation of the ancient usage of the device. It is consistent with references to writing along the staff by many (mainly French) authors. In a way, it may be called transposition by partial lines but "transposition" was not the essence. The scytale was simply a device to break lines into meaningless fragments.

If so, one does not have to specify the direction of writing. As indicated by Hulme [1898], the device could be used whether one writes diagonally or over the edges. Writing lengthwise, writing diagonally, or writing over the edges are all the same in that fragmentation of lines is attained. (It is even possible to write along and within the strip just for carrying or storing a message, without any intension of secrecy (Kelly (1998)).)

One further issue is information capacity. The transposition cipher by scytale as usually pictured today would be able to convey hundred letters or so at the most. This appears to be short of any practical usage of the scytale as an information carrier.

Scytale as a Transposition Cipher

At the beginning of the 20th century, Bazeries (1901) noted that no more than one letter should be written in a breadth of the strip in order to enhance security. Although it is likely that cryptologists in the 19th century may also have understood this, references to "letters" by Amyot or Plum may not have been based on such an insight.

Today's image of the scytale as a tool for transposition cipher appears to have been formed by the 19th century cryplotogists such as Bazeries.

Classical Sources

The title of this section remains "tentative" because my poor command of the classical languages does not allow me to make a conclusive statement based on the primary sources.

An expression like "reads around the staff" may be more amenable to the "writing over edges" interpretation, though line after line of writing along the staff may also be considered to be "around the staff." Expressions like "not forming letters" in a new scholarly translation of Plutarch into Japanese as well as "morcelées et mutilées" in the French translation of Aulus Gellius may be regarded as consistent with Porta's illustration.

The reader is kindly asked to provide me with some insight on this matter.

Further Sources

Brigitte Collard, "La cryptographie dans l'Antiquité gréco-romaine. III. Le chiffrement par transposition" (2004), FEC (Folia Electronica Classica), Louvain-la-Neuve, Numéro 7, janvier-juin 2004 (online) ... She examines descriptions of ancient sources including Plutarch, Aulus Gellius, and Ausonius in detail but does not appear to doubt that the scytale is for transposition cipher.

Kelly, T. (1998), "The Myth of the Skytale", Cryptologia, Vol. 22, no. 3, pp. 244-260 ... According to an abstract, this examines use of the word "skytale" from the 7th century B.C. to the 12th century A.D. and concludes that it was first used as a tool to carry or record a plaintext message, since the term was never mentioned in the context of secret communication before the 3rd century B.C.

Rose Mary Sheldon, "The Friedman Collection: An Analytical Guide" (pdf) ... The explanation of Item 3 (p.16-17) indicates at the time of Friedman's writing, the traditional definition of scytale as a tool for secrecy ("A mesage was written along the length of the stick") was accepted.



©2014 S.Tomokiyo
First posted on 4 December 2014. Last modified on 22 February 2017.
Articles on Historical Cryptography

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