?
Solved

Is GetHashCode for a file unique?

Posted on 2006-07-09
4
Medium Priority
?
738 Views
Last Modified: 2012-05-05
I'm using the following example to get the hash code for a file.  Is this hash code unique or could there be instances of overlapping?  If it's the later (instance of overlapping) help me understand how it occurs or if it's a rarity.

        OpenFileDialog1.FileName = ""
        OpenFileDialog1.ShowDialog()

        If OpenFileDialog1.FileName = "" Then Exit Sub

        Dim File_Stream As New System.IO.StreamReader(OpenFileDialog1.FileName)
        Dim File_Hash As Integer = File_Stream.ReadToEnd().GetHashCode()

        RichTextBox1.Text = File_Hash

        File_Stream.Close()
        File_Stream = Nothing
0
Comment
Question by:IUFITS
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
4 Comments
 
LVL 46

Accepted Solution

by:
aikimark earned 2000 total points
ID: 17069614
it is a rarity, but collisions can occur.  It only returns a 32-bit value, so there are only 4+ billion unique hash values.

http://msdn2.microsoft.com/en-us/library/system.string.gethashcode.aspx
0
 
LVL 3

Author Comment

by:IUFITS
ID: 17072665
Thanks for the answer.
0
 
LVL 46

Expert Comment

by:aikimark
ID: 17072769
Thanks for the points.  Glad I could help.

A much better hash alternative woulld be SHA-2/SHA160, SHA256, SHA1024.

MD5 is ok for non-sensitive applications, but NIST has put it on a "don't use for criticatl applications" list.
0
 
LVL 3

Author Comment

by:IUFITS
ID: 17072817
Very good, thanks for the additonal info!  :)  I'll keep that in mind.
0

Featured Post

Want to be a Web Developer? Get Certified Today!

Enroll in the Certified Web Development Professional course package to learn HTML, Javascript, and PHP. Build a solid foundation to work toward your dream job!

Question has a verified solution.

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

Article by: jpaulino
XML Literals are a great way to handle XML files and the community doesn’t use it as much as it should.  An XML Literal is like a String (http://msdn.microsoft.com/en-us/library/system.string.aspx) Literal, only instead of starting and ending with w…
If you're writing a .NET application to connect to an Access .mdb database and use pre-existing queries that require parameters, you've come to the right place! Let's say the pre-existing query(qryCust) in Access takes a Date as a parameter and l…
In this video we outline the Physical Segments view of NetCrunch network monitor. By following this brief how-to video, you will be able to learn how NetCrunch visualizes your network, how granular is the information collected, as well as where to f…
Monitoring a network: how to monitor network services and why? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the philosophy behind service monitoring and why a handshake validation is critical in network monitoring. Software utilized …
Suggested Courses

765 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