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Encryption - Password Sofware
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Source：Internet Author：Unknow Pubdate：2008-04-14
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lexington (Marine/Ocean)
16 Nov 05 18:57
Does anyone know of an Encryption - Password sofware package that provides HIGH security without significantly increasing the file size ?
Usage is to prevent 'third party' cracking when files are transmitted via a shared email-server. Adobe *.pdf and (obviously) Microsoft Office files are being accessed by the 'sever-spies'.
melone (Electrical)
16 Nov 05 19:08
Can you prevent the spies from accessing the server?
lexington (Marine/Ocean)
17 Nov 05 0:21
Regretably the worst offender is the owner/operator of the server !! Makes it difficult !!
PS Re-reading my post I see I have to learn to spell "sofTware".
IRstuff (Aerospace)
17 Nov 05 1:55
字串4
http://www.cren.net/crenca/onepagers/pgp2.html TTFN
lexington (Marine/Ocean)
17 Nov 05 6:12
Thanks IRstuff, I was aware of PGP although I've never used it upon the basis of increased file size, however, in reality I think it may be the only reasonable alternative. Thanks again for the input !
gravix (Computer)
18 Nov 05 20:21
I also recommend PGP.
If you truly need HIGH security, then the file size consideration should be waived. Much of the strength of encryption comes at a cost of additional storage space. Without increasing the file size at all (or using compression), the best you can get is a simple substitution cypher, every A is changed to C, every D is changed to X, and so on. Obviously this sort of thing can be broken very easily.
PGP is good for another reason -- it's open-source. If you want to, you can verify that it is secure by checking the code. With closed source software from commercial vendors, you are forced to rely on their promises.
字串5
johnwm (Computer)
22 Nov 05 2:35
You could consider WinZip (or one of its many competitors). They normally provide an encryption option and can be mad as self-extracting packages Good Luck
johnwm
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MrBananas (Electrical)
8 Dec 05 11:08
Encryption does not necessarily make the file size significantly larger. The reason for size increase is due to the fact that encryption algorithms are typically block encryption algorithms. RSA (asymmetric key-sender and recipient have different keys) and AES (symmetric key-same key used both ends) both require data to be processed in blocks which are powers of two large. If the data is not large enough to fill an entire block, it will be "padded" with fake data and encrypted. This is the reason for the apparent size increase. This usually only happens on the last block, so the max size increase you should see would be just a few hundred extra kilobytes, which on a large office or pdf file wouldn't make much difference. For example, I just encrypted a 3712KB file using 2048 bit RSA encryption, and the resulting encrypted file was 3794KB, hardly anything to worry about. 字串7
One thing you should know is that aysymmetric encryption such as used on PGP is orders of magnitude slower thatn symmetric key, which is why PGP is usually used to send/receive text, or exchange keys for a symmetric algorithm. Both methods are considered to be generally very secure, with the weak point usually being the user or the computer the data was encrypted on. A brute force attack on either (assuming a good key was used (i.e. randomly generated)) would be a waste of time.
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