Re: Cryptographic Functions

[Jeffrey Walton <noloader () gmail com>]

Hi Munyaradzi,

> When a passphrase is used a key in symetric
> cryptography, how does the pass phrase map to
> the key in an algorithm like AES

The passphrase should be derived using a KDF. KDFs includes salts and
iteration counts. Quite a few bodies offer guidance on KDFs - NIST,
RFC, IETF, and ANSI to name a few.

> how many letters correspond to 1 bit?
Don't know what you are asking here. The KDF should provide sufficent
'mixing' such that no information can be gained from 1 bit of output
(either 1 or 0 is equally probable). Otherwise, its not a very good
KDF.

Jeff

On 8/18/09, M.D.Mufambisi <mufambisi () gmail com> wrote:
> Hello people.
>
> 1. When a passphrase is used a key in symetric cryptography, how does
> the pass phrase map to the key in an algorithm like AES? ie....how
> many letters correspond to 1 bit? etc?
>
>
> Regards
>
> Munyaradzi Mufambisi

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