Article 31270 of alt.security: Path: nntpd.lkg.dec.com!crl.dec.com!crl.dec.com!bloom-beacon.mit.edu!newsfeed.internetmci.com!news.sprintlink.net!tank.news.pipex.net!pipex!dispatch.news.demon.net!demon!sunsite.doc.ic.ac.uk!sun.rhbnc.ac.uk!platon!fauzan From: fauzan@platon (Fauzan Mirza) Newsgroups: alt.2600,alt.security,sci.crypt Subject: Tiny IDEA encryption program (1/1) Followup-To: alt.security Date: 23 Oct 1995 14:10:25 GMT Organization: Royal Holloway, University of London Lines: 59 Message-ID: <46g7oh$5bs@sun.rhbnc.ac.uk> Reply-To: fauzan@dcs.rhbnc.ac.uk NNTP-Posting-Host: dns1.rhbnc.ac.uk Summary: IDEA file encryption program Keywords: encryption,binaries X-Newsreader: TIN [version 1.2 PL2] Xref: nntpd.lkg.dec.com alt.2600:118536 alt.security:31270 sci.crypt:45481 This is an updated version of the tiny IDEA program (first posted to sci.crypt in June 1995). Tiny IDEA is a tiny file encryption program (608 bytes). It uses the International Data Encryption Algorithm cipher (obviously) which is the symmetric cipher used in PGP. The passphrase can be upto 128 characters long (it could be much longer, this limit is user-defined). Because of the overwriting mechanism, tiny IDEA can also be used for secure file wiping (removing files such that advanced data recovery methods would be unable to retrieve the original file contents). Simply encrypt the file using a random string as the key (tap the keyboard in various places), then decrypt it using another random string, then encrypt again, then decrypt, and so on. One encrypt-decrypt sequence is sufficient to wipe the file, but will provide minimal security; I suggest between four and eight. The really paranoid among you can use four hundred. Technical details about the tiny IDEA program: Files are processed in place (effectively wiping the original). The passphrase is hashed using tandem Davies-Meyer (with IDEA). It uses 8 round IDEA in ciphertext feedback mode. The feedback is done on 8 byte blocks. The initialisation vector (IV) is set to zeros. Written in 8086 assembly (heavily optimised for size). The main improvements over the previous version are longer passphrases, byte ordering bug fixed, overwriting key and data information upon exit, and a slight speed improvement. This version is not compatible with the previous one. It is possible to implement a C program to decrypt tiny IDEA encrypted files and vice versa (using PGP IDEA source for example). Example IDEA 8086 source is available from: ftp://ftp.ox.ac.uk/pub/crypto/misc/idea86.zip It should soon be replaced by the updated IDEA routines containing IDEA, CFB, tandem DM, and a demo encryption program (ZIP file, 7387 bytes). begin 644 idea3.com MZ%@!NC4#OH``K`K`=`JLK#PM=`<\*W0(Z3P!Q@;A`_^MK#P-=`0\('7WQD3_ M`+0)ND<#S2&T"KI?`\TAN1``OF$#45:Q!+[O`[\'!/*E7E:Q!*V&X*OB^KX' M!%:+_N@%`;$$ON<#O_<#5_*E7UY6Z"T!B_>_YP.Y!`"M,P6KXOI?7E97L02M MAN"KXOJQ!+[W`_*E7HO^Z,T`L02^[P.__P-65_*E7U>^!P3H\@!>7[D$`*TS M!:OB^EZ#Q@A9XH._YP/HH0"X`CVZA`#-(7(,B]BT/[D`@+IW!,TA_;P3HI`"`/N$#`'437KD$`*V&X#,%JX;@ MB43^XO/K%8OW7[D$`*V+'8;[B5S^,\.&X*OB\5^#QPA9XKY;6E*X`4*Y___W MVLTA6;1`NG<$S2%R#('Y`(!T@[0^S2'K![I4`[0)S2$SP+]A`[D6`?*JPX/' M$+L(`(O#)`<\!G<*3K#HM%XHM5Y.L&BT7RBU7TL0G3X+$'T^H+ MPJO^PX#[-'7.P\8&Y@,(5XL=BTT"BVT$BWT&B]/H:0"+V*T#R*T#Z(O7Z%P` MB_B)#N(#B2[D`XO#,^B+QS/(B]7H10"+Z`/(B]'H/`"+R`/HB\$SV(O%,_@S M#N0#,R[B`_X.Y@-UM(O3Z!T`B]BM`^BM`\B+U^@0`(OX6)>)'8EM`HE-!(E% M!L-2K??B*\):=0JX`0`K1/XKPNL#%0``PTE$14$@6RM\+5T@/$9I;&4^)%!A 8 Programming/Security DOS/NetWare/Linux --------------------------------------