10 LET t$="Wonderful ZX Spectrum."
20 LET c$="a":REM more characters, more difficult for decript
30 LET CIFRA=1: LET DESCIFRA=-1
40 PRINT t$''
50 LET modo=CIFRA: GO SUB 1000
60 PRINT r$''
70 LET t$=r$: LET modo=DESCIFRA: GO SUB 1000
80 PRINT r$''
90 STOP
1000 REM Criptex
1010 LET p$="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890 .,;:()-"
1020 LET longPatron=LEN p$
1030 LET longTexto=LEN t$
1040 LET longClave=LEN c$
1045 LET k=0: LET r$=""
1050 FOR i=1 TO longTexto
1060 LET k=k+1: IF k>longClave THEN LET k=1
1070 LET x$=t$(i)
1080 FOR j=1 TO longPatron
1090 IF x$=p$(j) THEN LET delta=j: GO TO 1110
1100 NEXT j
1110 LET x$=c$(k)
1120 FOR j=1 TO longPatron
1130 IF x$=p$(j) THEN LET delta=delta+modo*j: GO TO 1150
1140 NEXT j
1150 IF delta>longPatron THEN LET delta=delta-longPatron: GO TO 1170
1160 IF delta<1 THEN LET delta=longPatron+delta
1170 LET r$=r$+p$(delta)
1180 NEXT i
1190 RETURN