no, not at all. even with a keyspace of 2^256, the number of possible plaintexts that make sense is an infinitely small portion of all plaintexts - you can say

no, not at all. even with a keyspace of 2^256, the number of possible plaintexts that make sense is an infinitely small portion of all plaintexts - you can say with reasonable certainty then, that only one plaintext, combined with the the key could produce that ciphertext. the only system that has this same property (as far as i know) would be the one-time-pad. my crypto is a bit rusty, so i may be wrong..