I keep on forgetting to correct my use of terms. The substitution cipher in the last postings is really a one-way hash function. That is, you can not reverse the ciphering process and get the, in this example, domain name. This is because more than one character is mapped to a single digit. In the demonstration grid all instances of 'a', 'g','m', and 's' are replaced with 1. And everything that is not between 'a' and 'x' is replaced with 0. This is a one-way hash. The most famous is the MD5.