Just wondering if you could: 1. Hash first on the device (SHA-2, no salt) after converting to common case and removing extraneous characters from contact data.

Just wondering if you could: 1. Hash first on the device (SHA-2, no salt) after converting to common case and removing extraneous characters from contact data. 2. Send hashes over secure connection (SSL, TLS). 3. Hash again on the server (SHA-2, salted with value known only to service provider) 4. Delete all data a reasonable time after comparison / mapping is done. This way, although it's not unbreakable, there are the advantages of: - Encrypted, pre-hashed data over the wire. - Easily comparable data on the server. - Reasonably secure server side storage as long as the salt is secured. Dumb idea?