Ok. Thanks. I have an SHA-1 hash of a file and the digest is
DA39A3EE5E6B4B0D3255BFEF95601890AFD80709. Is this160 bit? How does the
output map to 160 bits?
On 8/18/09, Shailesh Rangari <shailesh.sf (at) gmail (dot) com [email concealed]> wrote:
> Hi Munyaradzi,
>
> On Tue, Aug 18, 2009 at 2:02 PM, Jeffrey Walton <noloader (at) gmail (dot) com [email concealed]> wrote:
>
>> 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.
>
>
> I second that.
> Also, assuming that a strong Hash Function is being used, then it is
> difficult to ascertain how many letter(s) would correspond to 1 bit - for
> one of the essential properties of a Hash Function is that it takes in an
> 'Arbitrary' length of input(key, passphrase, message, etc) and converts it
> into a 'Unique', 'Fixed' length output (hash). A Key Len of 128, 256, 512
> Bit if hashed with SHA-1, then the output would necessarily be 160 Bits
> only.
>
>>
>>
>> Jeff
>>
>> On 8/18/09, M.D.Mufambisi <mufambisi (at) gmail (dot) com [email concealed]> 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
>> >
>>
>
DA39A3EE5E6B4B0D3255BFEF95601890AFD80709. Is this160 bit? How does the
output map to 160 bits?
On 8/18/09, Shailesh Rangari <shailesh.sf (at) gmail (dot) com [email concealed]> wrote:
> Hi Munyaradzi,
>
> On Tue, Aug 18, 2009 at 2:02 PM, Jeffrey Walton <noloader (at) gmail (dot) com [email concealed]> wrote:
>
>> 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.
>
>
> I second that.
> Also, assuming that a strong Hash Function is being used, then it is
> difficult to ascertain how many letter(s) would correspond to 1 bit - for
> one of the essential properties of a Hash Function is that it takes in an
> 'Arbitrary' length of input(key, passphrase, message, etc) and converts it
> into a 'Unique', 'Fixed' length output (hash). A Key Len of 128, 256, 512
> Bit if hashed with SHA-1, then the output would necessarily be 160 Bits
> only.
>
>>
>>
>> Jeff
>>
>> On 8/18/09, M.D.Mufambisi <mufambisi (at) gmail (dot) com [email concealed]> 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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