Except that they don't encrypt your data, you do. Probably would have helped to RTFA, huh bub? =p
I am not certain of there product is secure. After all, what they distribute are the keys for a group, or the algorithm to generate the keys. All one needs to do is join the group, and the entire group's communications will be in the clear.
I use that concept in software that I wrote. It has a header of four unsigned integers consisting of groupno,key1,key2,key3, where each field is an integer in the range 0..255.
Groupno selects a group from a previous randomly generated encryption keys.
Each individual group has 256 encryption keys (3DES) or key fragments(AES,other). It works by a) Select a group, b) select the first key, or fragment by indexing into the table to retrieve the encrypted 8 characters, do likewise with the 2nd key, and the 3rd key, and then from an divulged based table of fields, select the salt for cypher block chaining.
Yes, it is secure, no, it is not too too scalable (only 256 groups) However (256^4)*(!3) is the approximate number of individual combinations of possible encryption key combinations. Keep the group information confidential, and there you have it. You can always distribute the information as 60,36,24,35, or whatever. Is anything divulged?