> That's true if you combine multiple algorithms conventionally What I said is true no matter how you combine them, including in the manner you propose. > fli

> That's true if you combine multiple algorithms conventionally What I said is true no matter how you combine them, including in the manner you propose. > flip between supplying the output of each in rapid succession You've just exposed yourself to a possible related-key attack. Also, the effective entropy of your key could be halved simply by one of the PRNGs being compromised, so even absent a related-key attack, you'd better be using an encryption algorithm with a big key size. (BTW, it's 100% overhead, not 50% overhead.) (Oh, and if both algorithms happen to be compromised, the results are or might as well be 0-entropy. Yet again, somewhere along the way you end up trusting something.) > perhaps the flip in which PRNG is used for the output stream occurs at hard-to-predict points in time "Hard-to-predict" requires a secure random number generator. You've gone on to describe yet another ad-hoc random number generator that you would use in the construction of your random number generator. Cryptography is hard.