Word for Windows PW Cracker   by Independent (IND)

Word for Windows Password Cracker (R8) Copyright by Fauzan Mirza, 1995 This program attempts to recover the password for Word for Windows encrypted documents. Usage: WFWCD <DocumentPath> If the path to the protected document is not specified on the command line, the user will be prompted to enter it (also facilitating running from within Windows). Wildcards cannot be used in the document path. There is a short delay during loading and analysis of the document, after which a portion of the decrypted document and the password is displayed. Technical Explanation Word for Windows derives a 16 byte binary key from the password and cyclicly XORs this key with the plaintext. This is called a repeated key cipher and its weaknesses are well known. In versions 1 and 2, the key was stored along with the encrypted document (probably by accident). With a little intuition, it was trivial to retrieve the decrypted text or to remove the encryption from the document: Locate 16 bytes of pure key in the document header. Cyclicly XOR the key with the ciphertext. Marc Thibault used a similar routine in his public domain WORDUNP program. In version 6, the document file format was changed and the key was no longer stored in the file. This did not make it that much more difficult to solve though; someone with a little knowledge of cryptanalysis would be able to extract the plaintext from most encrypted documents: Load ciphertext into a 16 column buffer. For each key byte from 1 to 16, Let key byte be the most frequent character in column XOR'd with 32. Cyclicly XOR the key with the ciphertext. Although this may be able to solve most files, most of the time the user would need to correct guesses made by the routine. And if the document is fairly short, or doesn't contain enough spaces then it's guaranteed to fail. The new file format also made constructing a decrypted document quite difficult. WFWCD extends the above routine. It uses a much better algorithm to recover the plaintext, and then to recover the password. The decryption engine is based on the WP1 program, by Lyal Collins, but has been improved. It assumes that the document consists predominantly of lower case letters, and the letter frequencies are close to that of English. It may fail to solve documents in which these conditions are not satisfied. For example, if there is very little textual content in the file (less than 300 bytes) than it will fail because of the lack of data for analysis. Other Information WFWCD (Word For Windows Cracker Demo) was developed and tested using gcc under Linux, and was only recently ported to MSDOS. R8 is an indication of the revision number. I had plans for R9, but it would take too much time to complete and so I decided to release this preliminary version instead. If you'd like to contact me, my current email address is: Fauzan Mirza <[email protected]> Thanks to the following people to whom this program is dedicated: Hamid Moosavi, Christopher Wilkinson, John Godley, and IRON MAIDEN. WFWCD IS FREEWARE AND YOU ARE ALLOWED TO USE AND DISTRIBUTE THE PROGRAM PROVIDED THAT IT IS NEITHER USED FOR AIDING DISHONEST OR CRIMINAL ACTIVITY, NOR USED FOR PROFIT.