  Virtualization has become more important since cloud computing is getting
more and more popular than before. There is an increasing demand for security
among the cloud customers. AMD plans to provide Secure Encrypted Virtualization
(SEV) technology in its latest processor EPYC to protect virtual machines by
encrypting its memory but without integrity protection. In this paper, we
analyzed the weakness in the SEV design due to lack of integrity protection
thus it is not so secure. Using different design flaw in physical address-based
tweak algorithm to protect against ciphertext block move attacks, we found a
realistic attack against SEV which could obtain the root privilege of an
encrypted virtual machine protected by SEV. A demo to simulate the attack
against a virtual machine protected by SEV is done in a Ryzen machine which
supports Secure Memory Encryption (SME) technology since SEV enabled machine is
still not available in market.
