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.