Definition of checksum

Suppose that one byte in a buffer covered by the Internet checksum algorithm needs to be decremented (e.g., a header hop count field). Give an algorithm to compute the revised checksum without rescanning the entire buffer. Your algorithm should consider whether the byte in question is low order or high order. | Numerade

What Is Checksum? Guide to Learn Checksum | Simplilearn

Checksum: The Simplest to Calculate the Checksum for MD5 and SHA256