In what cases are hash sums used to ensure data integrity?

Hash sums are used to ensure data integrity in the following cases:

• File integrity verification during transfer or storage. For example, when downloading a file, you can compare its hash sum with a reference to ensure the file is not corrupted or altered.
• Change control in version control systems. Hash sums help determine if a file has been modified.
• Data authentication. In cryptography, hash sums are used to create digital signatures and verify authenticity.
• Error detection during data transmission. For example, in network protocols to check that data has not been corrupted.

Example: when downloading an OS ISO image, MD5 or SHA256 hashes are often provided so that the user can verify that the downloaded file matches the original.