How to create MD5 Checksums and validate a file in Linux

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This article will explain how to generate a MD5 Checksum on a file or list of files and also how to validate a file against a known MD5 Checksum.

What is a MD5 Checksum?

The MD5 checksum is a widely used cryptographic hash function that produces a 128-bit (16-byte) hash value. It’s commonly used to verify data integrity.

MD5 stands for ‘Message Digest algorithm 5’. The ‘checksum’ part of ‘MD5 checksum’ refers to the output produced by the MD5 function, a sequence of 32 hexadecimal digits.

When you download a file from the internet, it may come with an MD5 checksum. This is an alphanumeric string that acts as a unique identifier for that specific file. If even a single byte of the file changes, the MD5 checksum will also change, thereby indicating that the file is not the same as the original one.

It’s important to note that while MD5 is fast and efficient, it is no longer considered sufficiently secure for most cryptographic functions as it’s susceptible to hash collisions. Despite this, it remains widely used for non-cryptographic purposes, such as checksums for file integrity verification.

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Create and Validate MD5 Checksum on Linux

1. Generate MD5 Checksum on a single file

md5sum filename

2. Generate MD5 Checksum on multiple files

md5sum filename1 filename2 filename3

3. Generate MD5 Checksum and output to file

md5sum filename > md5.txt

4. Compare MD5 Checkum output file to current file in directory

md5sum -c md5.txt

Example of what a MD5 Checksum looks like

d4fdb933151cad1eb58e798d2874f8f6 send_file-

Frequently Asked Questions (FAQ)

Can I use MD5 checksum to encrypt a password?

No, while MD5 can be used for hashing passwords, it’s not recommended due to its vulnerabilities. MD5 is susceptible to collision attacks, where different inputs produce the same hash, reducing its security. For password storage, more secure cryptographic hash functions such as bcrypt or Argon2, which are specifically designed to be slow and computationally intensive to deter brute-force and rainbow table attacks, are recommended. Passwords should also be salted to further enhance security.

How do download and check MD5 checksum in a single command?

In Linux, you can download a file and check its MD5 checksum in one command using curl or wget and md5sum. For example:
curl -LJO | tee filename.tar.gz | md5sum -c checksumfile.md5

This command downloads the file from the URL, saves it as filename.tar.gz, and then pipes it to md5sum to verify the MD5 checksum listed in checksumfile.md5.

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