There are many different types of hash algorithms such as RipeMD, Tiger, xxhash and more, but the most common type of hashing used for file integrity checks are MD5, SHA-2 and CRC32. In such cases, it would be impossible to tell at a glance if two similar files are different or not, but the hash values would easily tell these files apart if they are different. In some situations, an encrypted file may be designed to never change the file size nor the last modification date and time (for example, virtual drive container files). If they are the same, then the transferred file is an identical copy. To ensure the transferred file is not corrupted, a user can compare the hash value of both files. Hashing is also used to verify the integrity of a file after it has been transferred from one place to another, typically in a file backup program like SyncBack. Without opening two document files to compare them word-for-word, the calculated hash values of these files will allow the owner to know immediately if they are different. One main use of hashing is to compare two files for equality. A hash algorithm can only be considered good and acceptable if it can offer a very low chance of collision.

If it does, this is known as a hash collision. Hashing is also a unidirectional process so you can never work backwards to get back the original data.Ī good hash algorithm should be complex enough such that it does not produce the same hash value from two different inputs. A hash function that does not do this is considered to have poor randomization, which would be easy to break by hackers.Ī hash is usually a hexadecimal string of several characters. The hash value can be considered the distilled summary of everything within that file.Ī good hashing algorithm would exhibit a property called the avalanche effect, where the resulting hash output would change significantly or entirely even when a single bit or byte of data within a file is changed. Hashing transforms this data into a far shorter fixed-length value or key which represents the original string. A file basically contains blocks of data. Hashing is an algorithm that calculates a fixed-size bit string value from a file. Two hash values (of the original file and its copy) can be compared to ensure the files are equal. If you are transferring a file from one computer to another, how do you ensure that the copied file is the same as the source? One method you could use is called hashing, which is essentially a process that translates information about the file into a code.

Introduction to Hashing and its uses Author: Conrad Chung, 2BrightSparks Pte.

What is crc sha