Securely compare customer lists from two parties

Say you're negotiating a deal with an external party and to be able to move forward you need to know how many customers do we have in common? Neither party is at this stage interested in sending their list of customers. My solution to this problem is by using the new MdFive function in SeoTools 5.0. MD5 which stands for Message Digest algorithm 5 is a widely used cryptographic hash function that was invented by Ronald Rivest in 1991....