A method performed by a virtual trusted platform module, vTPM on an execution platform, comprises the steps of obtaining (S11) encrypted information (encvTPMContext) and a first identifier (Salt), both associated with a virtual machine, VM to be executed; retrieving (S14), using the identifier from a trusted launch authority, TLA, at least a first secret portion (SlaKeystart), the first secret portion (SlaKeystart) being dynamically linked to the VM and dependant on at least a property of the VM; and decrypting (S16) the encrypted information (encvTPMContext) with a decryption key (EncKeystart) derived from at least the first secret portion (SlaKeystart) and a first measurement result (VmDigeststart) of at least the VM.