Hashes, salt, and pepper
Salt and Pepper
© Lead Image © topnat, 123RF.com
Cryptographic hash functions help you protect your passwords, but hashing is only secure if properly understood.
Hash functions are an integral part of computer science – and not just with databases and checksums. Hashes were originally intended for storing data efficiently in memory, but the hashing concept has evolved into a technique for securely storing passwords.
Linux writes the password hash values to the /etc/shadow file, which you can only read if you have root privileges. But even if you have the root password, you'll find it difficult to learn any useful access information. The function used to store the password hash values in etc/shadow is a one-way function, which means you can't work backward from the hash value to create the original password – at least in theory. As you'll learn in this article, attackers still sometimes manage to crack these supposedly irreversible hash functions.
What is a Hash?
The idea of a hash is simple: An address is calculated from the value that is to be stored. Suppose, for example, you need to store the four user names Fritz, Laempel, Max, and Moritz. A hash function would calculate a numeric value from these names.
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
KDE Linux Drops AUR
KDE Linux developers have dropped the Arch User Repository from the build pipeline due to security concerns; other distributions should consider doing the same.
-
California May Exempt Linux from Its Age-Verification Law
After backlash from the Linux community, California may be backing off on its promise to force all operating systems to verify age, but one platform may still have to comply.
-
Another Logic Bug Found in Linux Kernel
Qualys has discovered a vulnerability in the Linux kernel that can be used to elevate standard user privileges.
-
Ubuntu Core 26 Offers Game-Changing Enterprise Features
Ubuntu Core 26 could be a game-changer for organizations looking for increased security and reliability.
-
AI Flooding the Linux Kernel Security Mailing List
AI is giving Linus Torvalds a headache, but not in the way you might think.
-
Top Priorities for Open Source Pros Seeking a New Job
Professional fulfillment tops the list, according to LPI report.
-
Container-Based Fedora Hummingbird Designed for Agent-First Builders
Fedora Hummingbird brings the same approach to the host OS as it does to containers to level up security.
-
Linux kernel Developers Considering a Kill Switch
With the rise of Linux vulnerabilities, the kernel developers are now considering adding a component that could help temporarily mitigate against them… in the form of a kill switch.
-
Fedora 44 Now Gaming Ready
The latest version of Fedora has been released with gaming support.
-
Manjaro 26.1 Preview Unveils New Features
The latest Manjaro 26.1 preview has been released with new desktop versions, a new kernel, and more.