To learn whether or not the word “condemnation” does (or could) occur here, we proceed as in Fig. 169. The first of the five equations may have had either one of the relationships marked 1 and 2, and the second may have had either of the relationships marked 3 and 4. These two equations have a letter D in common, and it must not be impossible to form a combination which will represent both. This, as it happens, can be done in four different ways, marked 5, 6, 7, and 8, and we do not know which of the four is most likely. The third equation, which has four different letters, may have had any one of relationships 9, 10, and 11. These, fortunately, show two letters, N and C, which are also present in combinations 5, 6, 7, and 8, and with two common letters, there will not be so many possible adjustments as when we had only one. Nos. 9 and 10, for instance, cannot possibly combine with any one of combinations 5, 6, 7, and 8; both of these have demanded that the letters NC be in direct sequence, where the first four combinations will not permit this. We may begin, then, by discarding Nos. 9 and 10. But No. 11, which we have retained, demands of C and N only that they be on the same row. This is not permitted by any one of combinations 5, 6, or 7, and these also may be discarded. But No. 8 shows them on the same row; thus Nos. 8 and 11 may be further combined, and we have the combination marked 12. The fourth equation, another lineal one, may have had either of the relationships marked 13 and 14, and both of these will combine easily with the combination marked 12, so that again we have more than one possibility, as indicated under numbers 15 and 16. As to which of these is correct, the fifth equation, io = AD, is impossible to one, and has automatically been set up in the other.
We are safe, now, in making substitutions on the cryptogram. This means not only the five pairs originally identified, together with their reversals and possible reciprocals, but all others which can be derived from combination 16, such as
| Figure 170 O * * E N * E DE EC . . . . A T I M |
om = CA, or dm = CI, or en = DC, together with their reversals and possible reciprocals. Then, too, there will be many partial equations, such as those indicated in Fig. 170, where one letter of a pair can be identified. Usually time is saved by taking cryptogram pairs just as they come and filling in as many letters as possible; in this way, patterns are sometimes brought out, and thus we come back to step 1: the identification of more pairs. With the key-square beginning to shape up, the “chart of probable position” may be used to good advantage. For instance, what about the letters H and B which were very high in the frequency list?
Once a beginning is made, the cipher is broken, though just how rapidly we may proceed with the solution depends chiefly upon the manner in which the square has been filled. The presence of alphabetical sequences (either horizontal or vertical) will often enable us to complete the key-square independently of the cryptogram; but the badly mixed square must usually be built up to the very end, and we must sometimes be satisfied with one of the “equivalents” in place of the square originally used. If the student cares to make a fresh beginning of his own, this same cryptogram contains the word RECONSTRUCT.
The Playfair has been, in its day, a very effective cipher, and is still good for many purposes. It can be rendered much safer if subjected to the process called seriation. This process may be examined in Fig. 171. Here, the text is “Send
| Figure 171 S E N D D D S T O A R D A M M I A M O N M X S T E O N D A Y |
diamonds to Amsterdam Monday,” and the agreed seriation index is 5. The text is written in pairs of five-letter lines, so that each ten-letter segment forms five vertical pairs, SI, EA, NM, etc., and these are the pairs which undergo the digram encipherment (notice the treatment of the doubled S in the second group). If the key-square is that of Fig. 166, the first ten-letter segment is enciphered QK, UF, TG, SA, RS, and the cryptogram may be taken off in that order, or by taking the upper and lower lines separately: Q U T S R K F G A S. Seriation, it will be noticed, adds a transposition to a substitution, so that what we have here is combination cipher. This case, in short examples, is extremely difficult; it is mentioned only by way of general information, and is not included in the practice cryptograms which follow.
149. By NEMO. (Playfair. Probable words: ENEMY AGENTS).
OS CF WD OG DR AN PO AS OA DH SD EH XK FU CN DR PF UK SD.
150. By NEMO. (Playfair. Probable words: AUTHORIZED, EMERGENCY).
PK HL PG RI YH YN HQ IF YF GY ZL EB YF UK NK NG FL FG OL BD GX GK FC PK HG NV AC ZL
KH PK FG FK RZ FG RQ XO IB PB BD LE MV KG GY OL AD FK OR FC LK YN HL LK KZ IF EF AX
NG ON BV IK BI PK IO HQ IF AG LX YA FK AD YG KO AK EG TO OH BI RB OL ON KM FO PK KY
PR EF DZ IF AY QH CZ OK IQ WP FG LF DM CA VO GW PK NG KX KO LH AG NB RT NG KO KH HK
OX ML GP ML PB QD RB OH EB LH NK NG FC PK KY QS LH NE IQ WP FG.
151. By PICCOLA. ([Figure 164]; new external alphabets. THE, THIS, CHARACTER).
NF BJ HT MD NF WJ GD UC HN FW QI CE HP NF IA SE HS HS LG QA IY QD HV CC LB NF IA IA
CL GA RJ BD NM MA SY KU RD FT HC US HN GH VJ UA SY UL HN XJ EG QQ CJ LB NF KJ CN CS
UK GJ MD NF IA FK NQ GJ XX.
152. By PICCOLA. ("Slidefair." Probable word: DESCENT).
AA FS AF XY GJ BD UI AA PW GN IV QZ RC NK CC WA FT QQ PR GP TT WF PS JS QC HM DI XC
AH JP FB DC EW OX UG GP UI US CV GP MH QR OG JI ZR.
153. By DAN SURR. (Playfair. History: Detective Gettamann, investigating the
murder of Francis V. Bacon, well-known traveler, explorer, and
connoisseur, has found this message in an envelope addressed
to Wm. K. Pierce, former traveling companion of the deceased.
Death had occurred during sleep; caused by strangulation with
red silk thread. Only clues found: a few grains of sand on the
kitchen floor and what appears to be an oriental turban).
YG NG CR FV FZ RI OU KZ CW OW BQ GQ IH HL YW EG NG QM WX RT KP VE CA IG QI VD QI GN
GZ IZ QY QR HY NG XN AB AK OX NY WC WC TN OX DH NE IH IH YR IS QY WC HI UI UI IR QE
WS RW LG WR AB GW VW CA RQ XM ER QM RE CW ZI RQ XW QW GH YC AY YO VO NE RL PG CG WI
NX VW CA NX QM LH IG RQ WT GO UI GZ EG XN IW OU XT WO LH IG RQ XM WS QY TX IR IQ XM
OG DU AB RM AK UM RG ZR XA PM RW LD KG HI XK LC RT KP VE FO NX XK WR WS QY UR ZX YL
AT UI RH TR AV WS DH WQ PM AK IW OU WT DE IR WX RQ XZ SI GU QN IR XN IR YN IG GY TR
ZX YU RU YL IQ YA RU KG QM PD QM IY HA WS FE RW GH RB HA QI QM GI QC QR UL WV AB NX
GO HA FR IY QY BM QM YH NG IQ RU YL IQ BL PO QM RU GU IR TX SI GQ LQ DX XO EV BM CR
FV GV AB GE RZ GQ YH HA RW YM NE YM BL VW PS.