A method for cross-blockchain authentication, the method comprising: obtaining, by a subscribing client by using a cross-chain interaction end of a cross-blockchain interaction system, data from a second blockchain that is published by a publishing client, to use the data as an authentication data source, the cross-blockchain interaction system comprising the subscribing client, the publishing client, and the cross-chain interaction end, the subscribing client corresponds to a first blockchain, the publishing client corresponds to the second blockchain, the cross-chain interaction end is separately interconnected with the subscribing client and the publishing client and the first blockchain being used as a sidechain that is anchored to the second blockchain that is used as a main chain; receiving, by the subscribing client, data to be authenticated from the second blockchain; and performing, by the subscribing client, data authentication on the data to be authenticated based on the authentication data source and a data authentication rule configured on the first blockchain, characterized in that obtaining the data comprises: initiating, by the subscribing client, a subscription request to the cross-chain interaction end, wherein the subscription request is used to notify the cross-chain interaction end of a subscription condition, so that the cross-chain interaction end requests, based on the subscription condition, data on the second blockchain that satisfies the subscription condition from the publishing client; and obtaining, by the subscribing client, the data on the second blockchain that is published by the publishing client and that satisfies the subscription condition, to use the data as the authentication data source. obtaining, by a subscribing client by using a cross-chain interaction end of a cross-blockchain interaction system, data from a second blockchain that is published by a publishing client, to use the data as an authentication data source, the cross-blockchain interaction system comprising the subscribing client, the publishing client, and the cross-chain interaction end, the subscribing client corresponds to a first blockchain, the publishing client corresponds to the second blockchain, the cross-chain interaction end is separately interconnected with the subscribing client and the publishing client and the first blockchain being used as a sidechain that is anchored to the second blockchain that is used as a main chain; receiving, by the subscribing client, data to be authenticated from the second blockchain; and performing, by the subscribing client, data authentication on the data to be authenticated based on the authentication data source and a data authentication rule configured on the first blockchain, characterized in that obtaining the data comprises: initiating, by the subscribing client, a subscription request to the cross-chain interaction end, wherein the subscription request is used to notify the cross-chain interaction end of a subscription condition, so that the cross-chain interaction end requests, based on the subscription condition, data on the second blockchain that satisfies the subscription condition from the publishing client; and obtaining, by the subscribing client, the data on the second blockchain that is published by the publishing client and that satisfies the subscription condition, to use the data as the authentication data source. initiating, by the subscribing client, a subscription request to the cross-chain interaction end, wherein the subscription request is used to notify the cross-chain interaction end of a subscription condition, so that the cross-chain interaction end requests, based on the subscription condition, data on the second blockchain that satisfies the subscription condition from the publishing client; and obtaining, by the subscribing client, the data on the second blockchain that is published by the publishing client and that satisfies the subscription condition, to use the data as the authentication data source.