Smart contracts on Ethereum are fully self contained and any information or access to off-chain data is restricted. Tellor solves this problem by creating a system where parties can request the value of an off-chain data point (e.g. ETH/USD) and miners compete to add this value to an on-chain data bank, accessible by all Ethereum smart contracts. Inputs to a data series are secured by a network of staked miners. The main Tellor smart contract creates a time series of each requested data series and aims to become the standard source of high value data for decentralized applications. This oracle, “Tellor”, utilizes similar incentive mechanisms to other cryptocurrency systems through the issuance of Tellor’s token, Tributes, that are used to request a particular data series from miners.
DDK is a community platform that aims to create economic opportunities through the development of blockchain solutions. Since 2015, the DDK community claims to have contributed to a number of blockchain platforms.The DDK platform uses the Delegated Proof of Stake (DPoS) mechanism within its core. According to DDK, one of the advantages of a DPoS blockchain is that it depends on community members to participate in the maintenance and security of the platform so that each member’s participation provides benefit for all.