COMPLEMENTARITY ATTACKS AND CONTROL VECTORS

A control vector is a data structure that specifies the nature and rol e of an associated cryptographic key. The control vector is checked by software and cryptographic hardware in order to limit the range of pe rmissible operations to be undertaken with ciphertext produced with th e key. The linking of the control vector and cryptographic key is such that attempts to modify, or substitute, control vectors will cause th e subsequent processing to operate with a corrupted key, and hence ens ure protection of data encrypted with the genuine key. A potential att ack on the control vector approach is described in which the complemen t of the control vector is substituted. The manner in which such attac ks are thwarted by the IBM implementation of control vectors is also d escribed.