A method of verifying the integrity of a virtual machine in a cloud computing deployment, the method comprising: creating, at a virtual machine preparation entity, a virtual machine image derived from a trusted virtual machine, wherein the trusted virtual machine has a Keyless Signature Infrastructure, KSI, signature stored in a signature store; verifying, at a verification entity, whether a computation resource can be trusted, wherein the step of verifying comprises: receiving attested information about a boot of the computation resource, wherein the received information is protected using KSI or Quantum-Immune Keyless Signature with Identity, QSI; checking the received information using KSI or QSI; and confirming whether the computation resource can be trusted based on the received information; and if it is verified that a computation resource can be trusted: submitting the virtual machine image to the trusted computation resource; checking a signature of the virtual machine image against the stored signature of the trusted virtual machine; launching, at a virtual machine image launch entity, the virtual machine image on the trusted computation resource, and creating a KSI signature of the virtual machine image; and storing the signature of the virtual machine image in a signature store. creating, at a virtual machine preparation entity, a virtual machine image derived from a trusted virtual machine, wherein the trusted virtual machine has a Keyless Signature Infrastructure, KSI, signature stored in a signature store; verifying, at a verification entity, whether a computation resource can be trusted, wherein the step of verifying comprises: receiving attested information about a boot of the computation resource, wherein the received information is protected using KSI or Quantum-Immune Keyless Signature with Identity, QSI; checking the received information using KSI or QSI; and confirming whether the computation resource can be trusted based on the received information; and receiving attested information about a boot of the computation resource, wherein the received information is protected using KSI or Quantum-Immune Keyless Signature with Identity, QSI; checking the received information using KSI or QSI; and confirming whether the computation resource can be trusted based on the received information; and if it is verified that a computation resource can be trusted: submitting the virtual machine image to the trusted computation resource; checking a signature of the virtual machine image against the stored signature of the trusted virtual machine; launching, at a virtual machine image launch entity, the virtual machine image on the trusted computation resource, and creating a KSI signature of the virtual machine image; and storing the signature of the virtual machine image in a signature store. submitting the virtual machine image to the trusted computation resource; checking a signature of the virtual machine image against the stored signature of the trusted virtual machine; launching, at a virtual machine image launch entity, the virtual machine image on the trusted computation resource, and creating a KSI signature of the virtual machine image; and storing the signature of the virtual machine image in a signature store.