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 The IDEA Encryption Algorithm   Oliver Strutynski 16.12.1996

Реализация на Паскале алгоритма шифрования "IDEA".
IDEAUNIT is a unit for Turbo/Borland Pascal that allows programmers to add powerful encryption technology to their programs easily.



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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 ---------------------------end of file------------------------