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How to store 128 bit hash values optimaly in MS Access using ASP.NET

Posted on 2007-04-04
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Last Modified: 2012-05-05
I need to store the result of MD5 hashing to a database (MS Access) and currently the best option I understand is to convert it to a string and save that.  Is there a cleaner way of saving this data?

I start out with the value of hash1 from the following which produces an array of bytes (128 bit)

Dim MyHasher As New System.Security.Cryptography.MD5CryptoServiceProvider
Dim file1 As New FileStream("d:/customer/remcontshop/temp/upload.pdf", FileMode.Open)
Dim hash1 As Byte() = MyHasher.ComputeHash(file1)
file1.Close()
lblResult.Text = BitConverter.ToString( hash1 )

The value calculated for lblResult gives me the hash as a 16 bit hex string seperated by hyphens e.g.
"57-D9-95-B8-6F-23-CD-DB-78-E4-A1-10-24-BE-3C-C1"
I can store this to my database as text but if I can do it in a more efficient way, I'd prefer that.

Ideally I want it in a form where I can query it easily with SQL.  e.g.
SELECT * FROM hash_table WHERE hashvalue = "57-D9-95-B8-6F-23-CD-DB-78-E4-A1-10-24-BE-3C-C1"

Any ideas on how to get a more efficient result?
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Question by:Beamson
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3 Comments
 
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Expert Comment

by:Bob Learned
ID: 18849753
1) I would remove the dashes, since they are not needed, and only increase the size of your database.

2) There are ways to store the byte array in SQL Server, instead of the string.  This example writes an image to a BLOB:

Conserving Resources When Writing BLOB Values to SQL Server  
http://msdn2.microsoft.com/en-us/library/3517w44b.aspx

Here is another example that shows getting a byte array of data and writing to SQL Server:

Writing BLOB Values to a Data Source  
http://msdn2.microsoft.com/en-us/library/4f5s1we0.aspx

Bob
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Accepted Solution

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Jim Dettman (Microsoft MVP/ EE MVE) earned 375 total points
ID: 18850085
Well since you already have Hexadecimal pairs, there is no reason you could not store them in a 16 byte string that way.

JimD
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