You can achieve this by using the
HashContent processor or the
ExecuteStreamCommand processor to calculate the MD5 hash of the content and compare it to the contents of the prepared
*.md5 digest file, which you can read with
GetFile and then
ExtractText/RouteOnContent/RouteText to compare the MD5 value in a flowfile attribute with the contents of the file.
Here's a working example using separate signature files in the filesystem (e.g. 'filename.tgz' is the file and 'filename.sig' is a file containing the hash), and storing these in a distributed map cache.