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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 ;
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