That string is 160 bits... each hex char is worth 4 bits (though we
usually think of them in pairs of two, as an 8-bit byte).
-Jack Carrozzo
On Wed, Aug 19, 2009 at 2:31 AM, M.D.Mufambisi<mufambisi (at) gmail (dot) com [email concealed]> wrote:
> 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
>>> >
>>>
>>
>
usually think of them in pairs of two, as an 8-bit byte).
-Jack Carrozzo
On Wed, Aug 19, 2009 at 2:31 AM, M.D.Mufambisi<mufambisi (at) gmail (dot) com [email concealed]> wrote:
> 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
>>> >
>>>
>>
>
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