Non-deterministic wallet

These were the initial iterations of the Bitcoin clients; the wallets had randomly generated private keys. This type of wallet is being discontinued due to a major disadvantage, that the random keys are inaccessible if the wallet is lost. Since it is advisable to use a different address for every transaction in order to maintain anonymity on the network, with so many random keys, it becomes difficult to maintain and, hence, addresses became prone to re-use. Even though in the Bitcoin core-client, there is a wallet that is implemented as a type-0 wallet, its use is widely discouraged.