Verifying file integrity with MD5 checksums
Sounds techy and to a degree it is, but it's not hard to use freely available tools to ensure the files you send via the Internet, remain unchanged in transit. The problem with sending files via the Internet, is that they can change in transit without your knowledge. This is of concern when sending audio or data files destined for duplication or replication, so using MD5 checksum is one way of ensuring the files you send, are identical to the original copy stored locally.
Scenario
You are about to send a job to webs4cd for duplication or replication and to speed up time, you plan to send an image file rather than post a physical master. No problem for us, but how can you be sure the file that you send is identical to the one we actually receive. This is where MD5 checksum comes into play and proves a useful file to see if the file remains perfectly in tact.
There are various tools out there, but we are going to use a freeware version available here and it is called MD5 Check Utility v2.31 (at the time of writing)
To start with, download a copy of MD5 Check Utility v2.31 and run it (saving a copy somewhere for future use).
Create MD5 Checksum Process
So as to check the integrity of a file you are sending via the internet, follow these steps
- Run MD5 Checksum Utility program
- Click the radio button for 'Create MD5 Checksum'
- Click the 'Browse' button and locate the file you are planning to send via the internet
- Allow Notepad to open and click CTRL V (Edit > Paste) to paste the checksum
- Now, submit your file via the internet and provide recipient with the MD5 checksum
The checksum will look something like this C998D68A3696F66E595340C8EFBA1CFB
As shown in the image below, MD5 Checksum Utility will generate a MD5 checksum from the file and offer you the option to paste the code into notepad, which you should do.
Checksum Utility
Verifying a file integrity with MD5 checksum
The recipient of the file can the verity the integrity by checking the file you have sent, along with the MD5 checksum number you have supplied. If they match, the file is un-altered and as per the original, but if they mis-match, it means data loss has occurred in transit and the file can not be used. Follow the instructions below to verify a file with a checksum.
- Run MD5 Checksum Utility program
- Click the radio button for 'Verify MD5 checksum'
- Highlight the MD5 checksum and copy it (CTRL C) or (Edit > Copy) to windows clipboard
- In Md5 Checksum Utility program, click into the MD5 field and either CTRL V or click the 'Paste' button
- Click the 'browse' button and locate the file sent via the internet (in conjunction with provided MD5 hash)
- MD5 Checksum Utility will compare the file to the pasted MD5 code and confirm or deny file integrity
Successful MD5 Match
What to do if MD5 does not match
If you do not get a match, the file has been damaged in transit and must be considered faulty. Re-try sending the file again or consider using a different method of transit e.g yousendit, dropbox, ftp, email etc
