A firmware update method, wherein the method comprises: receiving, by user equipment, a first message sent by an update server, wherein the first message comprises first data and a signature of the first data; verifying, by the user equipment, the first message, and after the first message is successfully verified, obtaining, by the user equipment, digest data comprised in the first data, wherein the digest data comprises digest information of a differential installation package between a first installation package and a second installation package, and the digest data further comprises at least one of digest information of the first installation package or digest information of the second installation package, wherein the differential installation package is a differential part between the first installation package and the second installation package; receiving, by the user equipment, a second message sent by the update server, wherein the second message comprises the differential installation package; and verifying, by the user equipment, the digest data, and after the digest data is successfully verified, updating, by the user equipment, firmware of an embedded universal integrated circuit card, eUICC, based on the differential installation package; wherein the first installation package is an installation package corresponding to a current firmware version of the user equipment, and the second installation package is an installation package corresponding to an updated firmware version, wherein the verifying, by the user equipment, the first message comprises: decrypting, by the user equipment, the signature of the first data by using a pre-obtained public key of a certificate of the update server to obtain decrypted first data; calculating, by the user equipment, digest information of the first data; comparing, by the user equipment, the decrypted first data with the digest information of the first data; and if the decrypted first data is consistent with the digest information of the first data, determining, by the user equipment, that the first message is successfully verified. receiving, by user equipment, a first message sent by an update server, wherein the first message comprises first data and a signature of the first data; verifying, by the user equipment, the first message, and after the first message is successfully verified, obtaining, by the user equipment, digest data comprised in the first data, wherein the digest data comprises digest information of a differential installation package between a first installation package and a second installation package, and the digest data further comprises at least one of digest information of the first installation package or digest information of the second installation package, wherein the differential installation package is a differential part between the first installation package and the second installation package; receiving, by the user equipment, a second message sent by the update server, wherein the second message comprises the differential installation package; and verifying, by the user equipment, the digest data, and after the digest data is successfully verified, updating, by the user equipment, firmware of an embedded universal integrated circuit card, eUICC, based on the differential installation package; wherein the first installation package is an installation package corresponding to a current firmware version of the user equipment, and the second installation package is an installation package corresponding to an updated firmware version, wherein the verifying, by the user equipment, the first message comprises: decrypting, by the user equipment, the signature of the first data by using a pre-obtained public key of a certificate of the update server to obtain decrypted first data; calculating, by the user equipment, digest information of the first data; comparing, by the user equipment, the decrypted first data with the digest information of the first data; and if the decrypted first data is consistent with the digest information of the first data, determining, by the user equipment, that the first message is successfully verified. decrypting, by the user equipment, the signature of the first data by using a pre-obtained public key of a certificate of the update server to obtain decrypted first data; calculating, by the user equipment, digest information of the first data; comparing, by the user equipment, the decrypted first data with the digest information of the first data; and if the decrypted first data is consistent with the digest information of the first data, determining, by the user equipment, that the first message is successfully verified.