This method may be used, with some labor, on short words like THE, AND, etc. Parts of the key will appear whenever an assumed word is found in the message and the whole key may be assembled if enough of the parts are available. Even if only part of the key may be so recovered, it will always lead to the ultimate solution of the cipher by trial of the partially recovered key on the message letter by letter. As an example of recovery of a key by use of short common words, let us refer to the message of Case 7-a. There are twenty-four groups of three letters each in this message and we will try them against THE, ARE and YOU, assuming that the Vigenere cipher is used. 1 2 3 4 5 6 7 8 9 10 11 12 If OSB VOI GSW CYY ZSZ BVJ XLD OSY UVD YJL SQA HSI equals THE THE THE THE THE THE THE THE THE THE THE THE or ARE ARE ARE ARE ARE ARE ARE ARE ARE ARE ARE ARE or YOU YOU YOU YOU YOU YOU YOU YOU YOU YOU YOU YOU then A equals VLX CHE NLS JRU GLV IOF EEZ VLU BOZ FCH ZJW OLE or OBX VXE GBS CHU ZBV BEF XUZ OBU UEZ YSH SZW HBE or QEH XAO IEC EKE BEF DHP ZXJ QEE WHJ AVR UCG JEO 13 14 15 16 17 18 19 20 21 22 23 24 If BJV SFX DQB AII OHZ IVX JBF ESF JSC NLU CTW CSM equals THE THE THE THE THE THE THE THE THE THE THE THE or ARE ARE ARE ARE ARE ARE ARE ARE ARE ARE ARE ARE or YOU YOU YOU YOU YOU YOU YOU YOU YOU YOU YOU YOU then A equals ICR ZYT KJX HBE VAV POT QUB LLB QLY UEQ JMS JLI or BSR SOT DZX ARE OQV IET JKB EBB JBY NUQ CCS CBI or DVB URD FCH YUO QTF KHD LNL GEL LEI PXA EFC EES In column 5, we have, for YOU, the key BEF; column 6 gives the same key for ARE; column 10 gives the key FCH for THE and column 15 gives the same key for YOU; column 12 gives the key HBE for ARE and column 16 gives the same key for THE; column 23 gives the key EFC for YOU. The only possible key for the message is a five-letter one made up of the letters BEFCH or EFCHB or FCHBE or CHBEF or HBEFC. If the key in this case were a word, we would have no difficulty in determining it; as it is, there is no real difficulty in the matter as we may now divide the message into blocks of five letters and note that ZSZ (=YOU) form the 3d, 4th and 5th letters of a group. The corresponding key letters, BEF, are then the 3d, 4th and 5th letters of the key which must be CHBEF. This special solution for Case 7 depends so largely on the intuition of the operator in choice of a word that it is not, in general, advisable to use it unless the message is very short and the regular methods of analysis have been tried unsuccessfully. It is, however, a wonderfully short cut in difficult cases where the other methods fail.