1. A method for accessing a memory space allocated to a virtual machine, the method comprises: receiving a request from the virtual machine to generate, for another virtual machine, a memory credential associated with a certain memory space allocated to the virtual machine; generating, in response to the request, a cryptographically signed credential; sending the cryptographically signed credential to the other virtual machine; receiving from the other virtual machine an access request to access at least one memory entry within the certain memory space; and accessing the at least one memory entry, if the access request complies with the memory credential.