Identity authentication comprises: determining, in response to a request from a first device operated by a source user, that an identity authentication is to be performed for the source user; identifying a target user who is deemed to satisfy at least a preset condition, the target user being a user other than the source user; generating validation information to authenticate identity of the source user; sending the validation information to a second device operated by the target user; receiving a validation response from the first device operated by the source user; and performing identity authentication, including verifying whether the validation response received from the first device operated by the source user matches the validation information sent to the second device.