R – SharePoint files MD5 hash

md5sharepoint

We have a client who requires that all image files within SharePoint are stored in a manner that it can be shown they are a bit for bit copy of the originally uploaded file. Obviously, hashing the file would be able to show that when the file is retrieved.

What I haven't been able to find it any reference to someone implementing this functionality on a SharePoint image library. I've found numerous articles around implementing this generically in C#, but ideally I'd like to be able to do it on a standard SharePoint document/image library.

Does anyone have any suggestions as how best to go about doing this? Workflow comes to mind, but what do people think? Also, as a side to this, does anyone know whether or not SharePoint will store a bit for bit copy that will verify when we compare the checksum?

Best Answer

You can to implement a event handler which compute your file hash on upload and to store it in a metadata text field. It's a simple solution for your problem.

Related Solutions

Java – Getting a File’s MD5 Checksum in Java

There's an input stream decorator, java.security.DigestInputStream, so that you can compute the digest while using the input stream as you normally would, instead of having to make an extra pass over the data.

MessageDigest md = MessageDigest.getInstance("MD5");
try (InputStream is = Files.newInputStream(Paths.get("file.txt"));
     DigestInputStream dis = new DigestInputStream(is, md)) 
{
  /* Read decorated stream (dis) to EOF as normal... */
}
byte[] digest = md.digest();

Java – How to generate an MD5 hash in Java

The MessageDigest class can provide you with an instance of the MD5 digest.

When working with strings and the crypto classes be sure to always specify the encoding you want the byte representation in. If you just use string.getBytes() it will use the platform default. (Not all platforms use the same defaults)

import java.security.*;

..

byte[] bytesOfMessage = yourString.getBytes("UTF-8");

MessageDigest md = MessageDigest.getInstance("MD5");
byte[] theMD5digest = md.digest(bytesOfMessage);

If you have a lot of data take a look at the .update(xxx) methods which can be called repeatedly. Then call .digest() to obtain the resulting hash.

Best Answer

Related Solutions

Java – Getting a File’s MD5 Checksum in Java

Java – How to generate an MD5 hash in Java

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