checksumverification

Checksum verification is a data integrity practice that confirms whether a file has been altered or corrupted. It works by computing a checksum value from the file's contents using a checksum or hash function and comparing it to a checksum value published by the original source. A matching pair indicates the data likely remains unchanged; a mismatch suggests corruption during transfer, storage, or tampering.

Checksums and hashes come in two broad categories. Non-cryptographic checksums (such as CRC, Adler-32, and Fletcher) are designed to detect accidental errors. Cryptographic hashes (such as MD5, SHA-1, SHA-256, and SHA-512) provide stronger integrity checks but are not immune to intentional manipulation, especially for MD5 and SHA-1. Consequently, verification of critical software often relies on stronger hashes, and may be supplemented by digital signatures to prove origin and authenticity.

Practically, verification involves obtaining the expected checksum value from a trusted source, computing the checksum of the received file with an appropriate tool, and comparing the two values exactly. Tools include sha256sum or md5sum on Unix-like systems, Get-FileHash or CertUtil on Windows, and various third-party utilities. To reduce risk, users may check multiple algorithms, ensure the published value uses the correct encoding, and prefer sources that also provide a digital signature or secure delivery channel.