| Standard Spanish frequencytable | Table for Message Case4-a | ||||
| A | 111111111111111111111111111 | 27 | A | 1 | 1 |
| B | 11 | 2 | B | 1111111 | 7 |
| C | 111111111 | 9 | C | ||
| D | 1111111111 | 10 | D | ||
| E | 1111111111111111111111111111 | 28 | E | 1 | 1 |
| F | 11 | 2 | F | 11111 | 5 |
| G | 111 | 3 | G | ||
| H | 11 | 2 | H | 1 | 1 |
| I | 111111111111 | 12 | I | 111 | 3 |
| J | 1 | 1 | J | 1 | 1 |
| L | 1111111111 | 10 | L | 111 | 3 |
| M | 111111 | 6 | M | 1 | 1 |
| N | 111111111111 | 12 | N | 1 | 1 |
| O | 1111111111111111 | 16 | O | 111111 | 6 |
| P | 11111 | 5 | P | 111 | 3 |
| Q | 11 | 2 | Q | 111 | 3 |
| R | 111111111111111 | 15 | R | 11 | 2 |
| S | 11111111111111 | 14 | S | ||
| T | 11111111 | 8 | T | ||
| U | 1111111 | 7 | U | ||
| V | 11 | 2 | V | ||
| X | X | 11 | 2 | ||
| Y | 11 | 2 | Y | ||
| Z | 1 | 1 | Z | 1 | 1 |
Our first assumption might be that B = A and F = E but it is evident at once that in that case, S, T, U and V (equal to R, S, T and U) do not occur and a message even this short without R, S, T or U is practically impossible. By trying B = E we find that the two tables agree in a general way very well and this is all that can be expected with such a short message. The longer the message the nearer would its frequency table agree with the standard table. Note that if a cipher disk has been used, the alphabet runs the other way and we must count upward in working with a graphic table. Note also that if, in a fairly long message, it is impossible to coördinate the graphic table, reading either up or down, with the standard table and yet some letters occur much more frequently than others and some do not occur at all, we have a mixed alphabet to deal with. The example chosen for [case 6-a] is of this character. An examination of the frequency table given under that case shows that it bears no graphic resemblance to the standard table. However, as will be seen in [case 7-b], the preparation of graphic tables enables us to state definitely that the same order of letters is followed in each of a number of mixed alphabets.
General Remarks
Any substitution cipher, enciphered by a single alphabet composed of letters, figures or conventional signs, can be handled by the methods of case 6. For example, the messages under case 4-a and 5-a are easily solved by these methods. But note that the messages under case 4-b and 5-b cannot so be solved because several alphabets are used. We will see later that there are methods of segregating the different alphabets in some cases where several are used and then each of the alphabets is to be handled as below.
Case 6-a.
Message
QDBYP BXHYS OXPCP YSHCS EDRBS ZPTPB BSCSB PSHSZ AJHCD OSEXV HPODA PBPSZ BSVXY XSHCD
This message was received from a source which makes us sure it is in Spanish. The occurrence of B, H, P and S has tempted us to try the first two words as in case 4 and 5 but without result. We now prepare a frequency table, noting at the same time the preceding and following letter. This latter proceeding takes little longer than the preparation of an ordinary frequency table and gives most valuable information.
Frequency Table
| Prefix | Suffix | ||||
| A | 11 | 2 | ZD | JP | |
| B | 11111111 | 8 | DPRPBSPZ | YXSBSPPS | |
| C | 11111 | 5 | PHSHH | PSSDD | |
| D | 11111 | 5 | QECOC | BROA | |
| E | 11 | 2 | SS | DX | |
| F | |||||
| G | |||||
| H | 111111 | 6 | XSSJVS | YCSCPC | |
| I | |||||
| J | 1 | 1 | A | H | |
| L | |||||
| M | |||||
| N | |||||
| O | 111 | 3 | SDP | XSD | |
| P | 111111111 | 9 | YXCZTBHAB | BCYTBSOBS | |
| Q | 1 | 1 | D | ||
| R | 1 | 1 | D | B | |
| S | 111111111111 | 12 | YYCBBCPHOPBX | OHEZCBHZEZVH | |
| T | 1 | 1 | P | P | |
| U | |||||
| V | 11 | 2 | XS | HX | |
| X | 11111 | 5 | BOEVY | HPVYS | |
| Y | 1111 | 4 | BHPX | PSSX | |
| Z | 111 | 3 | SSS | PAB | |