IPG OTM expansion

I have a guess as to IPG's "OTP" expansion algorithm. The clue is the prime wheels. It reminded me of something I read in Kahn that was originally done with paper tape. Take two random streams, A and B. Their lengths are relatively prime. Let's use 1000 and 999. An expanded stream C is computed thus: C[i] = A[i % 1000] ^ B[i % 999] C thus does not repeat until 999000 values have gone past. Using more than two relatively prime wheels will produce very large streams. The key, of course, is that *the entropy does not increase*. I am sure that this sort of expansion is vulnerable to attack. It certainly does not warrant the name OTP. Am I close, Ralph?