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How Do Cryptographic Hash Functions Work?

With so much emphasis on computer and network security over the past few years, consumers and businesses alike have a renewed vigor when it comes to safeguarding their data and devices. Between the increasing prevalence of malware, more identity breaches than ever before and the ever-growing threat of foreign government-sponsored hackers, many computer users are exploring computer security at greater lengths – including cryptographic hash functions.

What is a Cryptographic Hash Function?

Although it doesn't necessarily roll off the tongue, cryptographic hash functions are an essential part of securing data in the 21st century. From a technical standpoint, the standard cryptographic hash function can easily be likened to the tamper-proof seal featured on many consumer products. If the package is opened by someone other than the purchaser – or end user – it's plainly evident from the broken seal.

Cryptographic hash functions work in much the same way. They provide a verifiable record or signature of the data contained within a particular file. It's important to differentiate a hash from a form of encryption. While the terms are often confused or used interchangeably, they are quite different.

Instead, think of a hash as a digest or, informally, a checksum. Encryption works by actually changing the contents of an encrypted file. Cryptographic hash functions work by compiling a summary – or digest – of the file. Unlike the process of encryption – where files can be decrypted with the correct key – cryptographic hash functions only work in one direction. Any modification to the file's contents would result in a corrupted hash.

Cryptographic Hash Functions in Use Today

Modern computing utilizes many different forms of cryptographic hash functions – and they're not focused on security.

File verification: One of the most common uses of hash functions today, this lets computer users verify the integrity of any file they've downloaded, copied or installed to their hard drive. In short, it ensures the authenticity and completeness of any new program.

Password security: Hash functions are also used to supplement password protection and security. When you enter your password into a site, it's hopefully converted from its original cleartext format to a hash string. If a hacker gains unauthorized access to the system, they'll only find a list of indecipherable hash strings instead of cleartext passwords and login information.

Digital document signing: One of the newest and most complicated uses of hash functions in modern computing involves digital document signing. It's the electronic equivalent of placing your signature or autograph onto an official contract or agreement – and acceptance of digital signatures is gaining momentum at an astounding speed.

Law enforcement: Investigators use hash strings and algorithms to track illegal P2P file sharers, too. By maintaining a comprehensive database of unique strings related to specific files, law enforcement can quickly and easily track the biggest offenders.

While it's a highly complicated process that becomes much more involved as you delve deeper, the underlying concept of a cryptographic hash function is rather basic and rudimentary. Moreover, it provides a framework for many different security platforms and systems that are currently in use today.


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