1. Error Detection vs Cryptography
A checksum is a small fixed-size value computed from digital data for the purpose of detecting accidental transmission or storage errors (like bit flips from electrical interference or truncated network downloads).
2. Common Checksum Algorithms
• Parity Check: Adds a single bit to verify whether the sum of 1s is even or odd.
• Longitudinal Redundancy Check (LRC): 2D parity over multi-byte data frames.
• Adler-32: Used in the zlib compression standard for fast validation.
• CRC32 / CRC32C: Cyclic Redundancy Checks used in Ethernet, PNG, ZIP, and modern file systems.
3. Checksums vs Cryptographic Hashes
Non-cryptographic checksums prioritize high speed (processing gigabytes per second with minimal CPU) but provide zero protection against intentional tampering. Cryptographic hashes (SHA-256) prioritize collision resistance against malicious attackers.