We present interpretations of type systems for secure information flow in Hoare logic, complementing previous encodings in binary (e.g. relational) program logics. Treating base-line non-interference, multi-level security and flow sensitivity for a while language, we show how typing derivations may be used to automatically generate proofs in the program logic that certify the absence of illicit flows. In addition, we present proof rules for baseline non-interference for object-manipulating instructions, As a consequence, standard verification technology may be used for verifying that a concrete program satisfies the noninterference property. Our development is based on a formalisation of the encodings in Isabelle/HOL.