LimeWire calculates the SHA1 digest of a downloaded file, then verifies that the file is not corrupt by making sure that the digest matches that which was obtained from the search result. All recent LimeWire versions can download a single file from multiple sources at once, even if some sources only had a partially downloaded file.

If LimeWire didn't check for the validity of the file's contents, one source could introduce bogus data and corrupt the download and the user won't know it. An SHA1 algorithm takes a message, or a long string of bytes, and produces a digest, or a much shorter string of bytes,
such that there is no efficient way to create another different message that would produce the same SHA1 digest.