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The ISAAC cipher: Difference between revisions
→{{header|Modula-2}}
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MOD : 734270227D36772A783B4F2A5F206266236978
MOD dcr : a Top Secret secret
</pre>
=={{header|Modula-2}}==
{{trans|Pascal}}
{{works with|ADW Modula-2|any (Compile with the linker option ''Console Application'').}}
I changed the identifiers to clearer ones and I changed the variables <code>a</code>, <code>b</code>, ..., <code>h</code> to an array, because they made my blood boil.
<lang modula2>
MODULE RosettaIsaac;
FROM Strings IMPORT
Length, Assign, Append;
FROM STextIO IMPORT
WriteString, WriteLn;
FROM Conversions IMPORT
CardBaseToStr;
CONST
MaxStrLength = 256;
TYPE
TMode = (iEncrypt, iDecrypt);
TString = ARRAY [0 .. MaxStrLength - 1] OF CHAR;
TCardIndexedFrom0To7 = ARRAY [0 .. 7] OF CARDINAL;
VAR
(* TASK globals *)
Msg: TString = 'a Top Secret secret';
Key: TString = 'this is my secret key';
XCTxt: TString = ''; (* XOR ciphertext *)
MCTxt: TString = ''; (* MOD ciphertext *)
XPTxt: TString = ''; (* XOR decryption (plaintext) *)
MPTxt: TString = ''; (* MOD decryption (plaintext) *)
Mode: TMode = iEncrypt;
HexTxt: TString;
(* ISAAC globals *)
(* external results *)
RandRsl: ARRAY [0 .. 256] OF CARDINAL;
RandCnt: CARDINAL;
(* internal state *)
MM: ARRAY [0 .. 256] OF CARDINAL;
AA: CARDINAL = 0;
BB: CARDINAL = 0;
CC: CARDINAL = 0;
PROCEDURE Isaac;
VAR
I, X, Y: CARDINAL;
BEGIN
CC := CC + 1; (* CC just gets incremented once per 256 results *)
BB := BB + CC; (* then combined with BB *)
FOR I := 0 TO 255 DO
X := MM[I];
CASE (I MOD 4) OF
0: AA := AA BXOR (AA SHL 13); |
1: AA := AA BXOR (AA SHR 6); |
2: AA := AA BXOR (AA SHL 2); |
3: AA := AA BXOR (AA SHR 16);
ELSE
END;
AA := MM[(I + 128) MOD 256] + AA;
Y := MM[(X SHR 2) MOD 256] + AA + BB;
MM[I] := Y;
BB := MM[(Y SHR 10) MOD 256] + X;
RandRsl[I] := BB;
END; (* FOR *)
RandCnt := 0; (* Prepare to use the first set of results. *)
END Isaac;
PROCEDURE Mix(VAR A: TCardIndexedFrom0To7);
BEGIN
A[0] := A[0] BXOR A[1] SHL 11; A[3] := A[3] + A[0]; A[1] := A[1] + A[2];
A[1] := A[1] BXOR A[2] SHR 2; A[4] := A[4] + A[1]; A[2] := A[2] + A[3];
A[2] := A[2] BXOR A[3] SHL 8; A[5] := A[5] + A[2]; A[3] := A[3] + A[4];
A[3] := A[3] BXOR A[4] SHR 16; A[6] := A[6] + A[3]; A[4] := A[4] + A[5];
A[4] := A[4] BXOR A[5] SHL 10; A[7] := A[7] + A[4]; A[5] := A[5] + A[6];
A[5] := A[5] BXOR A[6] SHR 4; A[0] := A[0] + A[5]; A[6] := A[6] + A[7];
A[6] := A[6] BXOR A[7] SHL 8; A[1] := A[1] + A[6]; A[7] := A[7] + A[0];
A[7] := A[7] BXOR A[0] SHR 9; A[2] := A[2] + A[7]; A[0] := A[0] + A[1];
END Mix;
PROCEDURE RandInit(Flag: BOOLEAN);
VAR
I, J: CARDINAL;
A: TCardIndexedFrom0To7;
BEGIN
AA := 0; BB := 0; CC := 0;
A[0] := 2654435769; (* $9e3779b9: the golden ratio *)
FOR J := 1 TO 7 DO
A[J] := A[0];
END;
FOR I := 0 TO 3 DO (* Scramble it *)
Mix(A);
END;
FOR I := 0 TO 255 BY 8 DO (* Fill in MM[] with messy stuff. *)
IF Flag THEN (* Use all the information in the seed. *)
FOR J := 0 TO 7 DO
A[J] := A[J] + RandRsl[I + J];
END;
END;
Mix(A);
FOR J := 0 TO 7 DO
MM[I + J] := A[J];
END;
END; (* FOR I*)
IF Flag THEN
(* Do a second pass to make all of the Seed affect all of MM *)
FOR I := 0 TO 255 BY 8 DO
FOR J := 0 TO 7 DO
A[J] := A[J] + MM[I + J];
END;
Mix(A);
FOR J := 0 TO 7 DO
MM[I + J] := A[J];
END;
END; (* FOR I *)
END;
Isaac(); (* Fill in the first set of results *)
RandCnt := 0; (* Prepare to use the first set of results *)
END RandInit;
(* Seed ISAAC with a given string.
The string can be any size. The first 256 values will be used. *)
PROCEDURE SeedIsaac(Seed: ARRAY OF CHAR; Flag: BOOLEAN);
VAR
I, M: CARDINAL;
BEGIN
FOR I := 0 TO 255 DO
MM[I] := 0;
END;
M := Length(Seed);
FOR I := 0 TO 255 DO
(* In case seed has less than 256 elements *)
IF I > M THEN
RandRsl[I] := 0
ELSE
(* Modula-2 strings are 0-based (at least, in this case). *)
RandRsl[I] := ORD(Seed[I]);
END;
END;
(* Initialize ISAAC with seed. *)
RandInit(Flag);
END SeedIsaac;
(* Get a random 32-bit value 0..MAXINT *)
PROCEDURE GetRandom32Bit(): CARDINAL;
VAR
Result: CARDINAL;
BEGIN
Result := RandRsl[RandCnt];
INC(RandCnt);
IF RandCnt > 255 THEN
Isaac();
RandCnt := 0;
END;
RETURN Result;
END GetRandom32Bit;
(* Get a random character in printable ASCII range. *)
PROCEDURE GetRandomChar(): SHORTCARD;
BEGIN
RETURN GetRandom32Bit() MOD 95 + 32;
END GetRandomChar;
(* Convert an ASCII string to a hexadecimal string. *)
PROCEDURE ASCII2Hex(Source: ARRAY OF CHAR; VAR OUT Destination: ARRAY OF CHAR);
VAR
I: CARDINAL;
NumbHex: ARRAY [0 .. 1] OF CHAR;
BEGIN
Assign('', Destination);
FOR I := 0 TO Length(Source) - 1 DO
CardBaseToStr(ORD(Source[I]), 16, NumbHex);
IF Length(NumbHex) <= 1 THEN
Append('0', Destination);
END;
Append(NumbHex, Destination);
END;
END ASCII2Hex;
(* XOR encrypt on random stream. *)
PROCEDURE Vernam(Msg: ARRAY OF CHAR; VAR OUT Destination: ARRAY OF CHAR);
VAR
I: CARDINAL;
OrdMsgI: SHORTCARD;
BEGIN
Assign('', Destination);
FOR I := 0 TO Length(Msg) - 1 DO
OrdMsgI := ORD(Msg[I]);
Append(CHR(GetRandomChar() BXOR OrdMsgI), Destination);
END;
END Vernam;
(* Get position of the letter in chosen alphabet *)
PROCEDURE LetterNum(Letter, Start: CHAR): SHORTCARD;
BEGIN
RETURN ORD(Letter) - ORD(Start);
END LetterNum;
(* Caesar-shift a character <Shift> places: Generalized Vigenere *)
PROCEDURE Caesar(M: TMode; Ch: CHAR; Shift, Modulo: INTEGER; Start: CHAR): CHAR;
VAR
N, IntOrdStart: INTEGER;
BEGIN
IF M = iDecrypt THEN
Shift := -Shift;
END;
N := LetterNum(Ch, Start);
N := N + Shift;
N := N MOD Modulo;
IF N < 0 THEN
N := N + Modulo;
END;
IntOrdStart := ORD(Start);
RETURN CHR(IntOrdStart + N);
END Caesar;
(* Vigenere mod 95 encryption & decryption. *)
PROCEDURE Vigenere(Msg: ARRAY OF CHAR; M: TMode; VAR OUT Destination: ARRAY OF CHAR);
VAR
I: CARDINAL;
BEGIN
Assign('', Destination);
FOR I := 0 TO Length(Msg) - 1 DO
Append(Caesar(M, Msg[I], GetRandomChar(), 95, ' '), Destination);
END;
END Vigenere;
BEGIN
(* (1) Seed ISAAC with the key *)
SeedIsaac(Key, TRUE);
(* (2) Encryption *)
Mode := iEncrypt;
(* (a) XOR (Vernam) *)
Vernam(Msg, XCTxt);
(* (b) MOD (Vigenere) *)
Vigenere(Msg, Mode, MCTxt);
(* (3) Decryption *)
Mode := iDecrypt;
SeedIsaac(Key, TRUE);
(* (a) XOR (Vernam) *)
Vernam(XCTxt, XPTxt);
(* (b) MOD (Vigenere) *)
Vigenere(MCTxt, Mode, MPTxt);
(* program output *)
WriteString('Message: '); WriteString(Msg); WriteLn;
WriteString('Key : '); WriteString(Key); WriteLn;
ASCII2Hex(XCTxt, HexTxt);
WriteString('XOR : '); WriteString(HexTxt); WriteLn;
ASCII2Hex(MCTxt, HexTxt);
WriteString('MOD : '); WriteString(HexTxt); WriteLn;
WriteString('XOR dcr: '); WriteString(XPTxt); WriteLn;
WriteString('MOD dcr: '); WriteString(MPTxt); WriteLn;
END RosettaIsaac.
</lang>
{{out}}
<pre>
Message: a Top Secret secret
Key : this is my secret key
XOR : 1C0636190B1260233B35125F1E1D0E2F4C5422
MOD : 734270227D36772A783B4F2A5F206266236978
XOR dcr: a Top Secret secret
MOD dcr: a Top Secret secret
</pre>
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