A method performed by a first application in a client apparatus to authenticate a second application in the client apparatus , the method comprising: when the first application receives an execution request from the second application , requesting authentication information of the second application for authenticating the second application from an authentication server ; obtaining the authentication information of the second application from the authentication server ; authenticating, by the first application , the second application using the authentication information; wherein the authentication information of the second application is signed with a private key of the authentication server , and wherein the authenticating of the second application comprises: authenticating the authentication information of the second application using a public key of the authentication server ; comparing a Hash-based Message Authentication Code, HMAC, value obtained from an application package, apk, file of the second application with an HMAC value included in the authenticated authentication information; extracting an execution file of the second application from each of the apk file of the second application and a cache memory, according to a result of the comparison; comparing the execution file extracted from the apk file of the second application with the execution file extracted from the cache memory. when the first application receives an execution request from the second application , requesting authentication information of the second application for authenticating the second application from an authentication server ; obtaining the authentication information of the second application from the authentication server ; authenticating, by the first application , the second application using the authentication information; wherein the authentication information of the second application is signed with a private key of the authentication server , and wherein the authenticating of the second application comprises: authenticating the authentication information of the second application using a public key of the authentication server ; comparing a Hash-based Message Authentication Code, HMAC, value obtained from an application package, apk, file of the second application with an HMAC value included in the authenticated authentication information; extracting an execution file of the second application from each of the apk file of the second application and a cache memory, according to a result of the comparison; comparing the execution file extracted from the apk file of the second application with the execution file extracted from the cache memory. authenticating the authentication information of the second application using a public key of the authentication server ; comparing a Hash-based Message Authentication Code, HMAC, value obtained from an application package, apk, file of the second application with an HMAC value included in the authenticated authentication information; extracting an execution file of the second application from each of the apk file of the second application and a cache memory, according to a result of the comparison; comparing the execution file extracted from the apk file of the second application with the execution file extracted from the cache memory. <EOS>