Tezos has a few technological differences when compared to Ethereum such as the use of dPoS, the unique ability to upgrade without the need of a fork, and formal verification which allows for code to be mathematically proven to be correct. This is particularly useful in the case of sensitive calculations needed in fields such as aircraft design and nuclear development.
Blockchains are secure by design and are an example of a distributed computing system with high Byzantine fault tolerance. Decentralized consensus has therefore been achieved with a blockchain. Blockchains solve the double-spending problem without the need of a trusted authority or central server, assuming no 51% attack (that has worked against several cryptocurrencies).
It is important investors realize not all exchanges and brokers that offer delivery of the underlying Bitcoin are created equal. Some firms have fallen victim to theft by hackers who have stolen Bitcoin belonging to clients whose money was held at the exchanges. Meanwhile, other Bitcoin exchanges have gone bankrupt (as in the case of Mt. Gox), as a result of fraud or mismanagement.
In 1998, Wei Dai published a description of "b-money", characterized as an anonymous, distributed electronic cash system. Shortly thereafter, Nick Szabo described bit gold. Like bitcoin and other cryptocurrencies that would follow it, bit gold (not to be confused with the later gold-based exchange, BitGold) was described as an electronic currency system which required users to complete a proof of work function with solutions being cryptographically put together and published. A currency system based on a reusable proof of work was later created by Hal Finney who followed the work of Dai and Szabo.