md5 collision

What encription algorithm should i use for replacing the md5 for hasing?I understand that it was release the source code of the application that could make md5 collision


Best regards,
julissa.leones@realcredits.com
master@poweroversoftware.com
http://www.poweroversoftware.com

julissa.leones@booomail.com wrote:

> What encription algorithm should i use for replacing the md5 for
> hasing?I understand that it was release the source code of the
> application that could make md5 collision

The best alternative at present is SHA256. If you want
less than 256 bits of hash, compute SHA256 and truncate
the result.

Note that the ability to produce collision pairs for MD5
is *not* fatal for applications like (1) password hashing
or (2) confirming that downloaded software matches the
official distribution, since both these uses
depend on the difficulty of finding a pre-image
for a specific hash.

--
Peter Pearson
To get my email address, substitute:
nowhere -> spamcop, invalid -> net

julissa.leones@booomail.com writes:

> What encription algorithm should i use for replacing the md5 for hasing?I understand that it was release the source code of the application that could make md5 collision


A little knowledge is a dangerous thing.
a) Linux does NOT password hash with MD5. It uses a horribly convoluted hash
function which uses md5 amongst many other things to create the hash.
b)One cannot create collisions. One can generate two files which have the
same md5 hash. One cannot create a second file with the same md5 hash as
a given file.
c) If you want to use the hash for other purposes, the recommendation is to
use sha256.

* Unruh <unruh-spam@physics.ubc.ca>
| b)One cannot create collisions. One can generate two files which
| have the same md5 hash. One cannot create a second file with the
| same md5 hash as a given file.

Care to re-phrase? The last two sentences contradict each other in my
understanding if interpreted literally.

| One can generate two files which have the same md5 hash.

Copy the file and it will have the same hash (of course)?

| One cannot create a second file with the same md5 hash as a given
| file.

I just did? Or do you (obviously?) mean 'a second file with different
contents than the first one'?

R'

Ralf Fassel <ralfixx@gmx.de> said:
>* Unruh <unruh-spam@physics.ubc.ca>
>| b)One cannot create collisions. One can generate two files which
>| have the same md5 hash. One cannot create a second file with the
>| same md5 hash as a given file.
....
>| One cannot create a second file with the same md5 hash as a given
>| file.
>
>I just did? Or do you (obviously?) mean 'a second file with different
>contents than the first one'?

Yep. So, it has been found out that it is relatively easy (or at least
much easier than it should have been) to create two distinct files with
the same MD5 checksum. But only if you create the second file somehow
based on the first one.

If you just have the md5 hash, it is still relatively hard to generate
data which would produce the same hash.
--
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julissa.leones@booomail.com wrote:
> What encription algorithm should i use for replacing the md5 for
> hasing?

SHA, depending on the security needed, SHA1 may be fine
if not SHA256
source code and test vectors are readily availble.


--
Pat

Ralf Fassel <ralfixx@gmx.de> writes:

>* Unruh <unruh-spam@physics.ubc.ca>
>| b)One cannot create collisions. One can generate two files which
>| have the same md5 hash. One cannot create a second file with the
>| same md5 hash as a given file.

>Care to re-phrase? The last two sentences contradict each other in my
>understanding if interpreted literally.

No they do not. In the first case, you can create two files which have the
same md5. In the second you are given a file and you have to find another
one with the same md5. In the first case neither of the two files is known
beforehand. In the second one is.
Now, it is not as inoccuous as it sounds. Since you can also take two given
files and all stuff to the end of them such that the two ammended files
have the same md5. thus one could say "I agree to pay you $10 $ and the
other "I agree to pay you $1000" afterwards, the two read

"I agree to pay you $10



^&^^%KJSH*(*"

and the other reads

"I agree to pay you $1000


NLK<>&*(^&)(*P><M OI
"
and that junk could be hidden in the huge amount to junk that Word for
example stores in the file.



>| One can generate two files which have the same md5 hash.

>Copy the file and it will have the same hash (of course)?

>| One cannot create a second file with the same md5 hash as a given
>| file.

>I just did? Or do you (obviously?) mean 'a second file with different
>contents than the first one'?

>R'

Pat Farrell <pfarrell@nospam.com> writes:

>julissa.leones@booomail.com wrote:
>> What encription algorithm should i use for replacing the md5 for
>> hasing?

>SHA, depending on the security needed, SHA1 may be fine
>if not SHA256
>source code and test vectors are readily availble.

Because sha1 is closely based on MD5 it is no longer trusted.
sha256 is recommended. Despite similar names, the algorithm is very
different as I understand.

Unruh wrote:

> In the first case neither of the two files is known
> beforehand. In the second one is.

When dealing with the first case, you create the first of the two files,
then the file IS known. Then you would be dealing with the second case.
Unless you create both files at the same time, there is no way the first
case can happen. You will always have a known file after the creation of
the first file and only the second case would be applicable after the
creation of the first file.

matt_left_coast <not@chance.org> writes:

>Unruh wrote:

>> In the first case neither of the two files is known
>> beforehand. In the second one is.

>When dealing with the first case, you create the first of the two files,
>then the file IS known. Then you would be dealing with the second case.

But you have to create them together. You cannot create one and then make
another which has the same md5.

>Unless you create both files at the same time, there is no way the first

YOu have to create them at the same time for the break to work. Ie, the
break uses both files in creating the break.


>case can happen. You will always have a known file after the creation of
>the first file and only the second case would be applicable after the
>creation of the first file.

No. You must create both at the same time.
Eg, lets say you take the MD5 of the first file and place that byte at the end of the second,
then take the md5 of the second (including the added byte) and place one byte of that at the end of
the first file, etc for 100 steps. (This is NOT how it is done but it
illustrates how you can have to create both files at the same time.)