From the recurrence of B, F and O, we may conclude that a single substitution alphabet was used for this message. If so and if the alphabet runs in the same order and direction as the regular alphabet, the simplest way to discover the meaning of the message is to take the first two words and write alphabets under each letter as follows, until some line makes sense:
| O B Q F O B P B R P |
| P C R G P C Q C S Q |
| Q D S H Q D R D T R |
| R E T I R E S E U S |
The word RETIRESE occurs in the fourth line, and, if the whole message be handled in this way we find the rest of the fourth line to read USTED POR EL MISMO ITINERARIO QUE MARCHO. The message was enciphered using an alphabet where A = X, B = Y, C = Z, D = A, etc. noting that as this message is in Spanish the letters K and W do not appear in the alphabet.
Case 4-b.
Message
HUJZH UIUPN OZYTS VQXMI SMOMX MQHUD UMREI SESJU AG
This is a message in Spanish. We will handle it as in [case 4-a], setting down the whole message.
| HUJZHUIU | PNOZY | TSV | QX | MISMO | MXMQHUDUMR | EIS | ESJUAG |
| IVLAIVJV | QOPAZ | UTX | RY | A=A | NYNRIVEVNS | FJT | FTLVBH |
| JXMBJXLX | RPQBA | VUY | SZ | OZOSJXFXOT | GLU | GUMXCI | |
| LYNCLYMY | SQRCB | XVZ | TA | PAPTLYGYPU | HMV | HVNYDJ | |
| MZODMZNZ | TRSDC | YXA | UB | QBQUMZHZQV | INX | IXOZEL | |
| NAPENAOA | USTED | ZYB | VC | RCRVNAIARX | JOY | JYPAFM | |
| OBQFOBPB | A=U | AZC | XD | SDSXOBJBSY | LPZ | LZQBGN | |
| PCRGPCQC | BAD | YE | TETYPCLCTZ | MQA | MARCHO | ||
| QDSHQDRD | CBE | ZF | UFUZQDMDUA | NRB | A=S | ||
| RETIRESE | DCF | AG | VGVARENEVB | OSC | |||
| A=Q | EDG | BH | XHXBSFOFXC | PTD | |||
| FEH | CI | YIYCTGPGYD | QUE | ||||
| GFI | DJ | ZJZDUHQHZE | A=O | ||||
| HGJ | EL | ALAEVIRIAF | |||||
| IHL | A=M | BMBFXJSJBG | |||||
| JIM | CNCGYLTLCH | ||||||
| LJN | DODHZMUMDI | ||||||
| MLO | EPEIANVNEJ | ||||||
| NMP | FQFJBOXOFL | ||||||
| ONQ | GRGLCPYPGM | ||||||
| POR | HSHMDQZQHN | ||||||
| A=E | ITINERARIO | ||||||
| A=D |
Here each word of the message comes out on a different line, and noting in each case the letter corresponding to A, we have the word QUEMADOS which is the key. The cipher alphabet changed with each word of the message.
A variation of this case is where the cipher alphabet changes according to a key word but the change comes every five letters or every ten letters of the message instead of every word. The text of the message can be picked up in this case with a little study.