Recently, the airdrop project Worldcoin has attracted much attention. Although first-tier exchanges such as OKX and Binance have announced the listing of their token $WLD, Worldcoin, as a project that issues airdrops to all mankind, faces a more arduous task of preventing witches, so it adopts iris authentication. In addition, the recently concluded Linea testnet event also introduced an identity authentication link for witch attacks. At present, the attitude of the project team towards witches is evident, and account authentication has become a required course for every project interaction person. This article will introduce several popular identity authentication and witch-proof projects, including World ID, Gitcoin Passport, Nomis, Degenscore and Sismo.