Solved

vb.net Decode a SHA1 hash

Posted on 2009-04-07
4
3,536 Views
Last Modified: 2012-05-06
I am using the function below to create an SHA1 hash of a username & password

now, given the username and the hash, how can i recover the password?

Private Function CreateHash(ByVal user As String, ByVal pass As String) As String
        Dim hashAlg As SHA1 = SHA1.Create
        Dim hashvalue() As Byte = hashAlg.ComputeHash(System.Text.Encoding.Default.GetBytes(UCase(user) & ":" & UCase(pass)))
        Dim hashstring As String = ""
        For Each b As Byte In hashvalue
            hashstring += b.ToString("x2")
        Next
        hashAlg = Nothing
        hashvalue = Nothing
        Return hashstring
    End Function

Open in new window

0
Comment
Question by:sgaggerj
  • 2
  • 2
4 Comments
 
LVL 8

Accepted Solution

by:
OBonio earned 500 total points
ID: 24088432
A hash is not asymmetric which means it is one way.  Once hashed, you can't, in theory, 'unhash'.  You use hashes by comparing.  ie, input data is hashed and compared to previously computed hashes.
0
 
LVL 1

Author Comment

by:sgaggerj
ID: 24088690
that's what i figured....
0
 
LVL 8

Expert Comment

by:OBonio
ID: 24094892
If you're trying to unhash, you could look up rainbow tables....
0
 
LVL 1

Author Comment

by:sgaggerj
ID: 24097591
Took a look and it seems a lot more time consuming that I want to spend (cpu cycle wise) on doing what i wanted.
I found a workaround.

Essentially i had a login w/ a 'remember me' box that saved the login info - but when the app is updated the settings get overwritten and the user needs to type in the login/pass again.

i added a field to my db table with the user/pass hash and store that locally instead in a separate file that never gets written over. more secure and gets the job done.

thanks!
0

Featured Post

Live: Real-Time Solutions, Start Here

Receive instant 1:1 support from technology experts, using our real-time conversation and whiteboard interface. Your first 5 minutes are always free.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

There are many Password Managers (PM) out there to choose from. PM's can help with your password habits and routines, but they should not be a crutch you rely on too heavily. I also have an article for company/enterprise PM's.
Worried about if Apple can protect your documents, photos, and everything else that gets stored in iCloud? Read on to find out what Apple really uses to make things secure.
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …

786 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question