[Cryptography] "Perpetual Encryption"

[Dave Howe]

On 29/03/2017 02:56, Allen wrote:
>
> Mi = sequence of message bits
> Ri = sequence of random bits
> Pi = sequence of bits from PRNG keyed by key K
>
> The encoder transmits Mi xor Ri, and Ri xor Pi.  The decoder generates
> Pi and recovers
> Mi = (Mi xor Ri) xor ((Ri xor Pi) xor Pi)
>
> But its certainly not clear from the whitepaper.

I must be missing something here - surely if you have (Mi XOR Ri) and
(Pi XOR Ri) the logical next step is (Mi XOR Ri) XOR (Pi XOR Ri) leaving
you with Mi^Pi or a normal PRNG stream cypher, with Ri redundant?