Rodney Joffe goes to great lengths to explain how Message Digest Version 5 (MD5) or Secure Hash Algorithm 1 (SHA-1) are useful tools for a merge/purge by proxy of e-mail addresses (“Merge/Purge of E-Mail Addresses,” Feb. 7). Gee, aren't e-mail addresses already unique? Wouldn't a third-party service bureau provide sufficient confidentiality to list owners?
I dedupe 10M to 20M e-mail addresses with a simple comparison in MS Excel or MS Access. Certainly, a service bureau can do a large-scale merge/purge without hashing. If their process isn't secure, I'd look for another vendor.
So, list owner A applies an algorithm; forwards a hashed file; compares; matches hashed records to master files; extracts hashed records; converts to e-mail addresses. Seems more complicated than it has to be. When I want to visit my next-door neighbor, I walk across the yard. I don't walk all the way around the block to get there.