A list of mediaeval cipher manuscripts

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This list is extracted from Bernhard Bischoff, Ubersicht uber die nichtdiplomatischen Geheimschriften des Mittelalters (Sonderdruck aus Mitteilungen des Instituts fur Osterreichische Geschichtsforschung Band LXII), Graz 1954.

Bernhard Bischoff (1906-1991) was the world's leading expert on palaeography and had an encyclopaedic knowledge of his subject. This monograph of 27 pages summarises examples of non-diplomatic mediaeval cipher writing known to him. It is clear that he did not know of any cipher system of the period which was not essentially a simple substitution cipher. Almost all of the manuscripts cited contain a few words and phrases of ciphertext inserted into normal manuscripts: he gives only one example of a manuscript written entirely in cipher.

Normal letters

Plaintext letters retained

Text written in vertical columns

Reversal of sentences

Reversal of words

Reversal of syllables

Mirror writing

Regular transposition of neighbouring letters

Anagramming

Insertion of null letters

Omission of letters

Substitution

Of vowels

By the following consonant

By the preceding consonant

By some other consonant

By the following vowel

By a neighbouring consonant

Reciprocal transposition

Replacement of each letter by the following letter

Replacement of each letter by the preceding

Replacement of abc by zxy (atbash)

Substitution of letters by other keys

Substitution by letters and numerals

Substitution by letters and symbols

Substitution by letters and deceptive symbols

Use of foreign alphabets

Greek

(Covered by Bischoff in another article, Byz. Zs 44 1951 34 ff.)

Hebrew

Square character, left to right

Rabbinical characters, left to right

Manufactured alphabets

Mixed Greek and Hebrew letters

Runes

Ogham

The alphabet of Aethicus Hister

Glagolitic

Cyrillic

Armenian

Invented alphabets

A

B

C

D1

D2

D1, D2

E

F

G

H

I

Predominantly invented alphabets

A

B

C

D

E

F The secret writing of Duke Rudolph IV of Austria

G

H

I

J

K

L

M

N

O

P

Q

Symbols mixed with Arabic numerals

A

B

C

D

E

F

G

H

Neums

Spanish neums mixed with letters

Frankish neums, symbols and letters

Numerical ciphers and related

Vowels replaced with numerals

Replacement with abbreviated ordinal numerals (pri, sec, ter...)

Replacement with the sequence x, xx, xxx, xl...

Replacement with Arabic numerals

A: 1 2 3 4 5

B: 5 4 3 2 1

C: 5 6 7 8 9

D: 1 2 0 4 X

Substitution of dots (variations on . : :.)

A

B

Substitution of G GG GGG...

Substitution of vertical or diagonal lines

A diagonal, similar to ogham

B vertical lines

Substitution of p with one to five underlinings

Replacement of the entire alphabet with numerals and the like

Replacement of the letters with their positional number

A Roman numerals

Arabic Numerals

Clofruna, clophruna

Iisruna, lagoruna, hahalruna, stofruna

A possible runic alphabet

Greek numerals representing alphabetical position

Discussed by Bischoff elsewhere: he notes that Trithemius revived this system. 'Chaldaic' or 'Greek' numeral representing alphabetical position

Replacement by 'Chaldaic' or 'Greek' numerals in grammatical order (i.e. vowels, liquids, plosives)

Other numerical keys

Pigpen cipher

Musical notes