• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 763
  • Last Modified:

Is GetHashCode for a file unique?

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
IUFITS
Asked:
IUFITS
  • 2
  • 2
1 Solution
 
aikimarkCommented:
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
 
IUFITSAuthor Commented:
Thanks for the answer.
0
 
aikimarkCommented:
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
 
IUFITSAuthor Commented:
Very good, thanks for the additonal info!  :)  I'll keep that in mind.
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Keep up with what's happening at Experts Exchange!

Sign up to receive Decoded, a new monthly digest with product updates, feature release info, continuing education opportunities, and more.

  • 2
  • 2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now