In the fourth table, I is clearly E and A=E. The fifth table shows T=14 and J=9. If we take T=E we find that we would have many letters which should not occur. On the other hand, if we take J=E then T=O and in view of the many E’s already accounted for in the other columns, this may be all right. It checks as correct if we apply the last three alphabets to the second word of our message, OSB, which deciphers NOW. Using these alphabets to decipher the whole message, we find it to read:
“M. B. Am now safe on board a barge moored below Tower Bridge where no one will think of looking for me. Have good friends but little money owing to action of police. Trust, little girl, you still believe in my innocence although things seem against me. There are reasons why I should not be questioned. Shall try to embark before the mast in some outward bound vessel. Crews will not be scrutinized so sharply as passengers. There are those who will let you know my movements. Fear the police may tamper with your correspondence but later on when hue and cry have died down will let you know all.”
The key to this message is CHBEF which is not intelligible as a word but if put into figures indicating that the 2d, 7th, 1st, 4th, and 5th letter beyond the corresponding letter of the message has been used the key becomes 27145 and we may connect it with the “personal” which appeared in the same paper the day before reading:
“M. B. Will deposit £27 14s 5d tomorrow.”
Case 7-b.
Message
| DDLRM | ERGLM | UJTLL | CHERS | LSOEE | SMEJU |
| ZJIMU | DAEES | DUTDB | GUGPN | RCHOB | EQEIE |
| OOACD | EIOOG | COLJL | PDUVM | IGIYX | QQTOT |
| DJCPJ | OISLY | DUASI | UPFNE | AECOB | OESHO |
| BETND | QXUCY | LUQOY | EHYDU | LXPEQ | FIXZE |
| PDCNZ | ENELQ | MJTSQ | ECFIE | ARNDN | ETSCF |
| IFQSE | TDDNP | UUZHQ | CDTXQ | IRMER | GLXBE |
| IQRXJ | FBSQD | LDSVI | XUMTB | AEQEB | YLECO |
| IYCUD | QTPYS | VOQBL | ULYRO | YHEFM | OYMUY |
| ROYMU | EQBLV | UBREY | GHYTQ | CMUBR | EQTOF |
| VSDDU | DAFFS | CEBSV | TIOYE | TCLQX | DVNLQ |
| XYTSI | MZULX | BAXQR | ECVTD | ETGOB | CCUYF |
| TTNXL | UNEFS | IVIJR | ZHSBY | LLTSI |
On the preliminary determination, we have the following count of letters out of a total of 385:
| A | 8 | L | 23 | J | 9 |
| E | 38 | N | 11 | Q | 22 |
| I | 19 | R | 14 | V | 9 |
| O | 21 | S | 20 | X | 13 |
| U | 24 | T | 21 | Z | 6 |
| Total | 110 | Total | 89 | Total | 59 |
| 28% | 23% | 15% |
Every letter except K and W occurs at least six times. We may say then that it is a substitution cipher, Spanish text, and certainly not Case 4, 5 or 6. We will now analyze it for recurring pairs or groups to determine, if it be Case 7, how many alphabets were used. The following is a complete list of such recurring groups and pairs with the number of letters intervening and the factors thereof. In work of this kind, the groups of three or more letters are always much more valuable than single pairs. For example, the groups, HOBE, OYMU, RMERGL and UBRE show, without question, that six alphabets were used. It is not necessary, as a rule, to make a complete list like the following: