AII ... AII 45 = 3×3×5 BK ... BK 345 = 23×3×5 CT ... CT 403 No factors CTW ... CTW 60 = 2×2×3×5 DL ... DL 75 = 3×5×5 ES ... ES 14 = 2×7 FJ ... FJ 187 No factors NP ... NP 14 = 2×7 OL ... OL 120 = 2×2×2×3×5 OS ... OS 220 = 11×2×2×5 OSB ... OSB 465 = 31×3×5 PO ... PO 105 = 7×3×5 SQ ... SQ 250 = 2×5×5×5 TLF ... TLF 80 = 2×2×2×2×5 TP ... TP 405 = 3×3×3×3×5 UV ... UV 115 = 23×5 XMKU ... XMKU 120 = 2×2×2×3×5 UV ... UV 73 No factors YJ ... YJ 85 = 17×5 The dominant factor is clearly 5, so we may consider that five alphabets were used, indicating a keyword of five letters. Writing the message in lines of five letters each and making a frequency table for each of the five columns so formed, we find the following: Frequency Tables Colum 1 Column 2 Column 3 Column 4 Column 5 A 11 A 111111111 A 1 A 1 A 11 B B 111 B 111 B B 1111111 C 1111111 C 1 C 111 C 1111 C D 11 D 11 D 1 D D 111 E 1111 E E 11 E 1111111 E F 111 F F 111111111 F 111 F 11111 G 111111111 G G 111 G 11 G 11 H 111 H 11111 H 111 H 111 H 11 I 11 I 11 I 1111111 I 11111111111111111 I 11 J 11111 J 1 J 111111 J J 111111111 K 111111 K 11111 K K 1 K 1 L L 1111111111111111111 L 11 L 11111 L 1 M M M 1111111 M 1111 M 111 N 1111111 N 111 N 1111 N N 11111 O 11111 O O 111111111 O 1 O P 1111111 P 1111111 P 11111111 P 1111 P Q 11111 Q Q Q 11 Q 111111 R R 1 R 1 R 111111 R 1