A method for executing an application in a cloud system, wherein the method comprises: a) receiving a request from a first user for executing an application in the cloud system; b) receiving , from the first user, user data of the first user related to the execution of the requested application; c) storing the received user data of the first user in a first storage area of a computing environment of the cloud system; d) in the computing environment , executing the requested application based on the stored user data of the first user to obtain an execution result; and e) storing the execution result in a second storage area of the computing environment , f) wherein, the access permission of the first user to the first storage area is a write-only permission, and the access permission of the first user to the second storage area is a read-only permission; and g1) wherein user data of the first user related to the execution of the application is data encrypted by the first user with a private key in a private key/public key pair of the first user, and the public key of the first user is stored in a data keystore of the cloud system in association with a user identity of the first user, the method further comprising: g2) obtaining a user identity of the first user from the first user; g3) obtaining, from the data keystore , a public key in a private key/public key pair of the first user corresponding to the obtained user identity of the first user; g4) storing the obtained public key of the first user in a third storage area in the computing environment ; and g5) in the computing environment , decrypting the received encrypted user data of the first user using the public key of the first user stored in the third storage area. a) receiving a request from a first user for executing an application in the cloud system; b) receiving , from the first user, user data of the first user related to the execution of the requested application; c) storing the received user data of the first user in a first storage area of a computing environment of the cloud system; d) in the computing environment , executing the requested application based on the stored user data of the first user to obtain an execution result; and e) storing the execution result in a second storage area of the computing environment , f) wherein, the access permission of the first user to the first storage area is a write-only permission, and the access permission of the first user to the second storage area is a read-only permission; and g1) wherein user data of the first user related to the execution of the application is data encrypted by the first user with a private key in a private key/public key pair of the first user, and the public key of the first user is stored in a data keystore of the cloud system in association with a user identity of the first user, the method further comprising: g2) obtaining a user identity of the first user from the first user; g3) obtaining, from the data keystore , a public key in a private key/public key pair of the first user corresponding to the obtained user identity of the first user; g4) storing the obtained public key of the first user in a third storage area in the computing environment ; and g5) in the computing environment , decrypting the received encrypted user data of the first user using the public key of the first user stored in the third storage area. g2) obtaining a user identity of the first user from the first user; g3) obtaining, from the data keystore , a public key in a private key/public key pair of the first user corresponding to the obtained user identity of the first user; g4) storing the obtained public key of the first user in a third storage area in the computing environment ; and g5) in the computing environment , decrypting the received encrypted user data of the first user using the public key of the first user stored in the third storage area. <EOS>