typical approach for encryption using keys?

you can create one key from one passphrase or several keys from one
passphrase or create several keys from some data and associate it with
one passphrase.
What is the typical approach used in encryption software?
One key for all files or data blocks or one key for each file/data
block?

with kind regards, Lars

Re: typical approach for encryption using keys?

In article <1182939635.869835.224340@w5g2000hsg.googlegroups.com>,
wrote:
>you can create one key from one passphrase or several keys from one
>passphrase or create several keys from some data and associate it with
>one passphrase.
>What is the typical approach used in encryption software?
>One key for all files or data blocks or one key for each file/data
>block?

Any time you reuse information in a key, you weaken the security
of the key, if there is any chance that someone might discover
the reuse. An insider, a burgler, a cryptoanalyst doing
differential cryptoanalysis, a visitor who happens to notice the
big "What hath God wrought?" sign on your wall...

Re: typical approach for encryption using keys?

roberson@hushmail.com (Walter Roberson) (07-06-27 14:30:16):

> > you can create one key from one passphrase or several keys from one
> > passphrase or create several keys from some data and associate it
> > with one passphrase.
> > What is the typical approach used in encryption software?
> > One key for all files or data blocks or one key for each file/data
> > block?

Whatever you need. If you encrypt all your data with the same key, then
all data will be disclosed upon compromise. This is your decision.


> Any time you reuse information in a key, you weaken the security of
> the key, if there is any chance that someone might discover the
> reuse. An insider, a burgler, a cryptoanalyst doing differential
> cryptoanalysis, a visitor who happens to notice the big "What hath God
> wrought?" sign on your wall...

Differential cryptanalysis? Why specifically that? Is it terribly
useful against today's ciphers?


Regards,
Ertugrul Söylemez.


--=20
Security is the one concept, which makes things in your life stay as
they are. Otto is a man, who is afraid of changes in his life; so
naturally he does not employ security.

Re: typical approach for encryption using keys?

On Jun 28, 2:50 am, Ertugrul Soeylemez
wrote:
>
> Whatever you need. If you encrypt all your data with the same key, then
> all data will be disclosed upon compromise. This is your decision.

On Jun 27, 4:30 pm, rober...@hushmail.com (Walter Roberson) wrote:
>
> Any time you reuse information in a key, you weaken the security
> of the key, if there is any chance that someone might discover
> the reuse.


thanks for your answers; I am more interested in how actual current
available software uses keys when encrypting folders for example, eg.
TrueCrypt; do they use one key for all of the files or several keys?

thanks, Lars