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Re^4: Compressing and Encrypting files on Windows

by tachyon (Chancellor)
on Nov 01, 2004 at 22:42 UTC ( [id://404444] : note . print w/replies, xml ) Need Help??

in reply to Re^3: Compressing and Encrypting files on Windows
in thread Compressing and Encrypting files on Windows

, why don't you tell us what you really feel?

Because I thought it would get reaped ;-) The OPs post obviously annoyed me. I have no problem with people being wrong. Like most people I spout rubbish from time to time, but I typically have the good grace to add an AFAIK, IMHO, perhaps, maybe or whatever. It was the authoratative presentation of absolutely incorrect information that set me off.



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Re^5: Compressing and Encrypting files on Windows
by MidLifeXis (Monsignor) on Nov 02, 2004 at 18:18 UTC

    Just a point - if you compress and then encrypt, you are encrypting known pieces of data (block headers, dictionaries, etc). Depending on the compression algorithm, this may give a large enough chunk of data to assist an attack against the encrypted data stream.

    All of this is IIRC, of course ;)


      As you say knowing that the first two bytes of a valid decrypt must be say the gzip header bytes 0x1f 0x8b does provide a small chink that can potentially be exploited. If you are that paranoid they are easy to hide. Making two passes with the encryption algorithm is one easy way.