The Syllabary cipher was introduced by G-MAN (Robert J Friedman) in the May-June 2012 issue of the Cryptogram magazine. It is based on a standard 10x10 Key-Square containing all 26 letters and all 10 digits, plus a number of 2-letter and 3-letter combinations. Here is the basic key-square with the rows and columns numbered 0 to 9.
0 1 2 3 4 5 6 7 8 9
0 A 1 AL AN AND AR ARE AS AT ATE
1 ATI B 2 BE C 3 CA CE CO COM
2 D 4 DA DE E 5 EA ED EN ENT
3 ER ERE ERS ES EST F 6 G 7 H
4 8 HAS HE I 9 IN ING ION IS IT
5 IVE J 0 K L LA LE M ME N
6 ND NE NT O OF ON OR OU P Q
7 R RA RE RED RES RI RO S SE SH
8 ST STO T TE TED TER TH THE THI THR
9 TI TO U V VE W WE X Y Z
Words can usually be represented in more than one way by row and column coordinates. For example: FRIEND could be represented as 35 70 43 24 59 20, or as 35 75 28 20, or as 35 75 24 60, etc.
To encrypt a message:
(1) choose a key word or phrase, grouping the letters so that all groups are made of letter combinations from the basic key-square. For example "secret" could be grouped as SE C RE T.
(2) Put the key into the beginning of a 10x10 table, removing any repeated groups, and fill the rest of the table by copying the unused groups from the basic key-square. One extra requirement is that the digits must always be preceded by the same letter as in the basic key-square, 1 must always be preceded by A, etc.
(3) Number the rows and columns of the table in some arbitrary order, for example 7854320196 and 8905673214.
Here is the result for the example ordering and the key SE C RE T.
8 9 0 5 6 7 3 2 1 4
7 SE C 3 RE T A 1 AL AN AND
8 AR ARE AS AT ATE ATI B 2 BE CA
5 CE CO COM D 4 DA DE E 5 EA
4 ED EN ENT ER ERE ERS ES EST F 6
3 G 7 H 8 HAS HE I 9 IN ING
2 ION IS IT IVE J 0 K L LA LE
0 M ME N ND NE NT O OF ON OR
1 OU P Q R RA RED RES RI RO S
9 SH ST STO TE TED TER TH THE THI THR
6 TI TO U V VE W WE X Y Z
(4) Encode the plaintext by using row-column coordinates from the table. For example the plaintext "A secret message" could be encoded as:
80 52 79 75 76 09 14 14 77 38 52
as e c re t me s s a g e
yielding the ciphertext: 80 52 79 75 76 09 14 14 77 38 52 .
This type of cipher is usually difficult to solve; a fairly long crib should be provided. Easier to solve versions may be constructed by numbering the rows and columns in 0-9 order, or by using the key 'A' which gives just the basic key-square. If the rows and columns are numbered in the standard 0-9 order, the cipher is usually labeled "known coordinates, unknown keysquare". If the key is just the letter 'A', the cipher is usually labeled "unknown coordinates, known keysquare". Otherwise the cipher is labeled "unknown coordinates, unknown keysquare".
The length suggested by the ACA for this cipher is 110-154 ciphertext pairs.
Links: Encode-decode Syllabary cipher , Interactive syllabary solver