IDEA for Pascal
===============

IDEAUNIT is a unit for Turbo/Borland Pascal that allows programmers
to add powerful encryption technology to their programs easily.

If you have any comments or bug reports please send an eMail to
either olistrut@geocities.com (preferred) or olistrut@aol.com.

IDEAUNIT exports four routines that can be used for data encryption
and decryption using the IDEA-Algorithm.

The functions encryptFile and decryptFile provide an easy-to-use
interface for encrypting entire files. They require three parameters
and are to be called the following way:

        PROGRAM idea_encryption;
        USES IdeaUnit;

        VAR ideaResult:Byte;
            inFileName, outFileName, password: STRING;
        BEGIN
           { Get filenames and password first }
           ideaResult:=encryptFile(inFileName, outFileName, password);
           IF ideaResult<>0 then Writeln('IO-Error')
        END. {idea_encryption}


        PROGRAM idea_decryption;
        USES IdeaUnit;

        VAR ideaResult:Byte;
            inFileName, outFileName, password: STRING;
        BEGIN
           { Get filenames and password first }
           ideaResult:=decryptFile(inFileName, outFileName, password);
           IF ideaResult<>0 then Writeln('IO-Error')
        END.

Both functions return 0 when executed successfully, if there is an
file error they return the value of ioResult.
encryptFile does not only encrypt the file and writes it to disk,
it also writes a header to the file, indicating that the file was
encrypted with the IDEA algorithm and also saving the file size of the
input files.
I have seen other implementations of the IDEA cypher that did not save
any information about the file size but they couldn't restore the
file size when decrypting files because IDEA always encrypts 64 bit
blocks.
However the header does not affect the security of the encryption.
If you know of any standard file format for idea encrypted files
please inform me so that I can include this in a future release of
the unit.

There are two more procedures that allow you to encrypt/decrypt a
single block of data (data blocks for IDEA are 64 bit).

They are called the following way:

  encryptBlock(inBlock,
               outBlock {both of type tblock64},
               key {of type tkey128});
  decryptBlock(inBlock,
               outBlock {both of type tblock64},
               key {of type tkey128});

tBlock64 and tKey64 are defined in the unit. outBlock is a VAR
parameter.
tBlock64 is an Array[1..4] of word that should be filled with your
data and tkey128 is an array[1..8] of word that is filled with your
key. The encryption key and the decryption key are the same. If you
already have word data you can simply fill the inBlock array with
your data, otherwise (like if you have byte data) the data can be
converted to a block in any way you like to, but be sure to use
correct conversion in both ways. It would be best te check out your
conversion (data->block and block->data) without encryption first
and include encryption when your conversion works.

If your are not sure how to do the conversion have a look at the
procedures str2Block and Block2Str in the unit.

The following example shows how to encrypt the word data (0,1,2,3)
with the key (1,2,3,4,5,6,7,8) (64 bit data and a 128 bit key).

PROGRAM encrypt_word_data;
USES ideaunit;

VAR block : tblock64;
    i     : Byte;

CONST key:tkey128=(1,2,3,4,5,6,7,8);

BEGIN
  WriteLn('IDEA-Encryption');
  WriteLn('===============');
  { Set data array }
  block[1]:=0; block[2]:=1; block[3]:=2; block[4]:=3;
  { encryption: source data is overwritten }
  encryptBlock(block,block,key);
  Write('Encrypted data:  ');
  FOR i:=1 TO 4 DO
      Write(block[i],'  ');
  { decryption: encrypted data is overwritten }
  decryptBlock(block,block,key);
  Write('decrypted data:  ');
  FOR i:=1 TO 4 DO
      Write(block[i],'  ');
END.


LEGAL STUFF
===========

The IDEA-Unit is copyright (c) 1996 Oliver Strutynski
olistrut@geocities.com or olistrut@aol.com
For the newest version check out
 http://members.aol.com/olistrut/idea.htm.
This program and the sourcecode may be used freely for non
commercial purposes.
If you modify the source code please include a notice that is was
derived from my original unit and include the link to the web site
mentioned above. Also if you modify the source code, you have to make
clear that the new unit is _NOT_ my original IDEA unit.
If you want to redistribute this unit (like on an FTP server or a BBS
please send me an eMail so that I can notice you if there are any
changes to the unit.

This has to be said:
I assume no liability for damages resulting from the use of
this software, even if the damage results from defects in this
software, and I make no representations concerning the
merchantability of this software or its suitability for any specific
purpose.  It is provided "as is" without express or implied warranty
of any kind.
Because certain actions may delete files or render them
unrecoverable, I assume no responsibility for the loss or
modification of any data.

Remember that the IDEA algorithm is patent protected by Ascom-Tech AG.
No license fees are required for non-commerical use.  Commerical users
should contact
Ascom Systec AG, Dept CMVV, Gewerbepark, CH-5506, Magenwil,
Switzerland, idea@ascom.ch


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