I'd also recommend you take a look at the SDI Toolkit Extension from Search Discovery. They added functionality that might be of interest to you. It is a one-way hash but will hash to consistent values.
Here is their description:
One Way Hash
Converts a data element to a consistent obfuscated string.
One way hashing is commonly used to obfuscate sensitive information for analytics purposes. Hashing an email address or a customer id will return the same obfuscated value every time for tracking purposes.
user@example.com => 4da3a5736c67e46036f26146662a6e9491176a63de36b49b7ed2c5b47b37e96e