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From: rossum on 21 Feb 2010 07:26
On Sat, 20 Feb 2010 07:27:33 -0500, ?Ari ? <AriSilverstein(a)army.com>
wrote:

>On Mon, 15 Feb 2010 15:27:10 +0100, Rafael wrote:
>
>> I looking for a free program for WinXP that
>> cryptic ascii text into a file.txt, with algorithms
>> robust and one or more keyfile.
>> The program should read contents of file.txt
>> encrypt it and save the same file.
>>
>> Thanks
>>
>> Regards
>
>Xpost to sci.crypt boyz
The sci.crypt eminent, senior and well respected persons need to know
a bit more.

Who are you trying to protect the data from? ROT13 will probably hide
text from Great Aunt Mildred, but not from Great Aunt Esther who works
for GCHQ. Guvf vf fbzr EBG13 grkg.

Do you require the output to be ASCII text? Vigenère will do that but
is not very secure. Base-64 will turn bytes into ASCII but takes up
more space; does the cyphertext have to be the same length as the
plaintext or can it be longer?

Do you just need encryption or do you need authentication as well? In
most real life cases you need both. GCM mode does both in one,
alternatively CBC or CTR mode will do the encryption with HMAC-SHA256
for the authentication. GCM mode is relatively new while CBC, CTR and
HMAC are all well established.

For a free program you could write one yourself. RC4 is absurdly easy
to program, though obsolescent and vulnerable. Any self-written
program is likely to contain exploitable errors, even if you program
the actual algorithm correctly. Again, what resources are likely to
be deployed against you? Even RC4 is secure enough if you want to
stop your ten year old kid brother reading your files.

For a free program try TrueCrypt which has a reasonable reputation:
www.truecrypt.org

rossum

From: Maaartin on 9 Mar 2010 21:50
On Mar 9, 11:54 pm, WTShaw <lure...(a)gmail.com> wrote:
> I've done it again! While some crypto algorithms work cross-platform
> (Mac vs.Windoze), it is because formats are not encrypted.

No, it's just because they know they should not care. The simplest and
(most of the time) best way is to consider a file like a sequence of
bytes, not trying to find out what they mean. This way you get a
program working on any system and without hopelessly corrupting binary
files.

In case you need to transfer files from one system to another, than
you can do the conversions. But it has nothing to do with crypto. Even
ftp I only use in binary mode, sometimes I get bad line endings but
most programs do not care, and if the do,
I can convert them afterwards.
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