A checksum is a small, fixed-size value calculated from larger data to detect accidental corruption during storage, transmission, or processing. Checksums are fast integrity checks, not protection against intentional tampering. section 13.3.1
Use a checksum to investigate data mismatches across system boundaries:
- Calculate and store or transmit the checksum when the data is generated. section 13.3.1
- Recalculate the value when the data is received or read, then compare it with the original. section 13.3.1
- Treat a mismatch as evidence of likely alteration or corruption, such as an incomplete write, bit flip, or faulty transmission. section 13.3.1
Verifying a downloaded file
A download site publishes file.exe with CRC32 checksum A12F3B4C. Recomputing the received file's CRC32 and matching A12F3B4C indicates a likely-correct download; a mismatch signals possible corruption. section 13.3.1
File: file.exe CRC32 Checksum: A12F3B4C
Inspect the compact file-and-checksum listing used to demonstrate integrity verification. section 13.3.1
