Out of annotated programs proof carrying code systems construct and prove verification conditions that guarantee a given safety policy. The annotations may come from various program analyzers and must not be trusted as they need to be verified. A generic verification condition generator can be utilized such that a combination of annotations is verified incrementally. New annotations may be verified by using previously verified ones as trusted facts. We show how results from a trusted type analyzer may be combined with untrusted interval analysis to automatically verify that bytecode programs do not overflow. All trusted components are formalized and verified in Isabelle/HOL.
