title: Comparing SHA-256 checksums: how many characters do I need to check?
body: <p>Checksums are useful for verifying that a file, such as a downloaded dmg, has not been changed. But it's tedious to examine the entire checksum, since a SHA-256 checksum has 64 hex characters. Fortunately, the algorithm is designed such that two files with a small difference in content will have very different checksums.</p>
  <p>Still, I want to be sure, so just how many characters do I need to compare to safely verify that two files are identical? Is it sufficient to compare, say, the first or last 5 characters?</p>