asked on

Hash Algorithm

Hi,
I am doing a program which will encrypt and decrypt a word.

Say for example input is :Hello

The code should encrypt and dcerypt the same.

I have been asked to implement md5 hash algorithm.

Can anyone give me a code which will implement the aboove using this algorithm.

Also let me know how we will decrypt the same.

Regds

NickAtBOM

check out

http://userpages.umbc.edu/~mabzug1/cs/md5/md5.html

for the code and help...

MadYugoslav

Try to search net for it (for example www.google.com).
There are pleanty of sites with that problem.

ASKER CERTIFIED SOLUTION

MDarling

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Masterdumbo

MD5 sum algorithm is an hasing algorithm , which clearly says that u can create check sum out of a sequence of bytes , this checksum would be unique any two given sequence bytes of a max length.

for eg:
y = f(x) where f(x) is the md5sum function that is a one way function.
u cannot do f inverse of x it will not be equal y

ie u cannot get back thye message from the checksum.

one way you can do this is as follows;

y= md5sum(x)
then y will be a 128 bit sequence.

next time you want to check do y1=md5sum(x1)

if (y1==y)
then x is equal to x1

Hope this will be of some help to your problems

Axter

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KangaRoo

Hi MasterDumbo, welcome to Experts-Exchange.

The answer you proposed is in essence a duplication of an earlier comment (stating that an MD5 encrypted string can not be decrypted).

Although at first glance it may seem that the question is answered, the problem gurukg faces is probably not solved. More important than answering the immediate question as it was formulated, is it to find a solution to the problem behind it.

Regards,
Frans

gurukg102498

ASKER

Hi,
Thanks to all for suggesting nice solutions. I am working on this. Once thru, will award you ponis.

Meanwhile is there no way to Decrypt the same ?

Regds

MDarling

NO there is no way to decrypt - it's one way.

For trivial comparison look at the square function.

f(x) = x * x

f(-3) = (-3) * -(3) = 9

f(3) = 3 * 3 = 9

Different inputs - same output - you cannot determine the input from the output.

MD5 is similarly one way - although the chance of 2 messages producing the same output is infinitessimal. It is possible.

Regards,
Mike.

3rsrichard

You may be getting sidetracked here.
It is clearly possible to encrypt and decrypt a word, or any amount of text,
for example with AES, twofish, "raindoll", and many others. You can
find a large supply here
http://www.eskimo.com/~weidai/cryptlib.html

The trouble you're having here is that "md5 hash algorithm" or
any hash algorithm isn't intended to be used to encrypt/decrypt.

If someone gives you a word and you use md5 to do a hash on it
you will get a number. The useful feature is that no one is likely to
find another word which would give the same number. A hash is
useful for checking to see if someone knows the right password,
and it's important that it isn't easy to go backward.

amp072397

Hello everyone.

I don't like having to do this, but attempts have been made to get gurukg to update his questions.

Questions Asked 21
Last 10 Grades Given A B B B B B C C C C
Question Grading Record 11 Answers Graded / 11 Answers Received

Please clean then up, gurukg, and be sure you do award points on this question as you have promised.

Thanks!
amp
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griessh

I suggest to accept "MDarling" comment(s) as an answer. She/he gave the first reasonable answer to the question.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!
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Werner

Netminder

Moondancer

This was finalized today by EE Moderator. Thanks for your help here, Werner, sorry it too me so long to find this in my inbox.
:)
Moondancer - EE Moderator

griessh

Once it's in a moderator's list, I trust that it gets resolved ;-)

======
Werner

Moondancer

Very true, Werner, thanks. The list keeps growing.
:) Moondancer - EE Moderator