Bifid cipher: Difference between revisions

160 GOSUB 200"ENCRYPT

165 PRINT M$M$"FOR "W" X "W" POLYBIUS:": M$ = CHR$ (13): FORIFOR I =1TOW 1 TO W:? PRINT , MID$ (K$,(I - 1) * W + 1,W): NEXT

170 PRINT "ENCRYPTED: "E$

180 GOSUB 300"DECRYPT

190 PRINT "DECRYPTED: "U$;: RETURN

200 GOSUB 400 : L = LEN (A$):E$ = "": U$ = "" : IF NOT L THEN RETURN

210 FOR I = 1 TO L

220 C = ASC ( MID$ (A$,I,1)) : IF X(C) AND Y(C) THEN U$ = U$ + CHR$ (C)

230 NEXT I

240 L = LEN (U$) : IF NOT L THEN RETURN

250 FOR I = 1 TO L : C = ASC ( MID$ (U$,I,1)) : A(I) = X(C) : A(I + L) = Y(C) : NEXT I

260 FOR I = 1 TO L * 2 STEP 2:E$ = E$ + MID$ (K$,(A(I) - 1) * W + A(I + 1),1): NEXT I

270 RETURN

300 GOSUB 400 : L = LEN (E$):U$ = "": IF NOT L THEN RETURN

310 FOR I = 1 TO L:C = ASC ( MID$ (E$,I)):B(I * 2 - 1) = X(C) : B(I * 2) = Y(C): NEXT I

320 FOR I = 1 TO L:U$ = U$ + MID$ (K$,(B(I) - 1) * W + B(L + I),1): NEXT I

330 RETURN

400 IF K$ = P$ AND LEN (K$) THEN RETURN

410 IF XY THEN FOR I = 0 TO 255:X(I) = 0:Y(I) = 0: NEXT I

420 IF NOT XY THEN DIM X(255),Y(255),A(512),B(512) : XY = 1

430 IF K$ = "" THEN FOR I = 1 TO 25:K$ = K$ + CHR$ (I + 64 + (I > 9)): NEXT I

440 L = LEN (K$):W = INT ( SQR (L - 1) + 1):I = 1:N = 1:K = ASC ("0")

450 FOR X = 1 TO W

460 FOR Y = 1 TO W

470 C$ = MID$ (K$,I,1) : IF C$ = "" THEN FOR C = K TO 255: IF X(C) THEN NEXT C : STOP

480 IF C$ = "" THEN C$ = CHR$ (C) : K$ = K$ + C$ : K = C + 1

490 C = ASC ( C$): Y(C) = Y:X(C) = X:I = I + 1: IF C$ = "J" THEN N = 0

500 NEXT Y,X

510 IF N THEN Y( ASC ("J")) = Y( ASC ("I")):X( ASC ("J")) = X( ASC ("I"))