Many of the uses of a True RNG fall into the general category of
generation, without persistent storage, of a value that is
different with high probability from any value determined
otherwise. A value that is different with high probability from
any value determined otherwise is very useful in cryptographic
protocols. For example, under classic CBC encryption with
multiple messages enciphered with the same key, an IV needs to
be distinct from a previous IV (which is necessary to conceal a
possible repeat of the plaintext), and distinct from the XOR of
the first block of plaintext with any value that has or will
ever enter the input of the block cipher (which is necessary to
ensure confidentiality of that first block of plaintext under
the assumption that all other plaintext is known). "Without
persistent storage" requirement rules out a Pseudo RNG, and
greatly simplify things: in the case of PRNG, persistent storage
needs to be made confidential and/or integrity-protected, which
is plain impossible on a regul