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+PACKET cryptograf DEFINES (* Autor: J.Liedtke *)
+ (* Stand: 01.10.80 *)
+ crypt ,
+ decrypt :
+
+TEXT VAR char , in buffer, out buffer ;
+INT VAR in pos , key index ;
+DATASPACE VAR scratch space := nilspace ;
+FILE VAR in, out;
+
+PROC crypt (TEXT CONST file, key) :
+
+ open (file) ;
+ initialize crypt (key) ;
+ WHILE NOT eof REP
+ read char ;
+ crypt char ;
+ write char
+ PER ;
+ close (file) .
+
+crypt char :
+ char := code (( character + random char + key char ) MOD 250) ;
+ IF key index = LENGTH key
+ THEN key index := 1
+ ELSE key index INCR 1
+ FI .
+
+character : code (char) .
+
+random char : random (0,250).
+
+key char : code (key SUB key index) .
+
+ENDPROC crypt ;
+
+PROC decrypt (TEXT CONST file, key) :
+
+ open (file) ;
+ initialize crypt (key) ;
+ WHILE NOT eof REP
+ read char ;
+ decrypt char ;
+ write char
+ PER ;
+ close (file) .
+
+decrypt char :
+ char := code (( character - random char - key char ) MOD 250) ;
+ IF key index = LENGTH key
+ THEN key index := 1
+ ELSE key index INCR 1
+ FI .
+
+character : code (char) .
+
+random char : random (0,250) .
+
+key char : code (key SUB key index) .
+
+ENDPROC decrypt ;
+
+PROC initialize crypt (TEXT CONST key) :
+
+ INT VAR random key := 0 ;
+ FOR key index FROM 1 UPTO LENGTH key REP
+ random key := (random key + code (key SUB key index)) MOD 32000
+ PER ;
+ initialize random (random key) ;
+ key index := 1
+
+ENDPROC initialize crypt ;
+
+PROC open (TEXT CONST source file) :
+
+ in := sequential file (input, source file) ;
+ getline (in, in buffer) ;
+ in pos := 1 ;
+ out := sequential file (output, scratch space) ;
+ out buffer := "" .
+
+ENDPROC open ;
+
+PROC close (TEXT CONST source file) :
+
+ IF out buffer <> ""
+ THEN putline (out, out buffer)
+ FI ;
+ forget (source file, quiet) ;
+ copy (scratch space, source file) ;
+ forget (scratch space) .
+
+ENDPROC close ;
+
+BOOL PROC eof :
+
+ IF in pos > LENGTH in buffer
+ THEN eof (in)
+ ELSE FALSE
+ FI
+
+ENDPROC eof ;
+
+PROC read char :
+
+ IF in pos > 250
+ THEN getline (in, in buffer) ;
+ in pos := 1 ;
+ read char
+ ELIF in pos > LENGTH in buffer
+ THEN in pos := 1 ;
+ getline (in, in buffer) ;
+ char := ""13""
+ ELSE char := in buffer SUB in pos ;
+ in pos INCR 1
+ FI .
+
+ENDPROC read char ;
+
+PROC write char :
+
+ IF char = ""13""
+ THEN putline (out, out buffer) ;
+ out buffer := ""
+ ELSE out buffer CAT char
+ FI ;
+ IF LENGTH out buffer = 250
+ THEN putline (out, out buffer) ;
+ out buffer := ""
+ FI .
+
+ENDPROC write char ;
+
+ENDPACKET cryptograf ;
+
+
+
+
+