A (polynomial-sized) circuit in this context is a sequence of DAGs whose nodes are binary logic gates where the nth DAG infers 1 output bit from n input bits, s

A (polynomial-sized) circuit in this context is a sequence of DAGs whose nodes are binary logic gates where the nth DAG infers 1 output bit from n input bits, such that some polynomial bounds the size of the graphs of the sequence. See https://en.wikipedia.org/wiki/Circuit_complexity https://en.wikipedia.org/wiki/Circuit_complexity The class of circuits in question is P/poly which includes BPP (which includes P, the class of polynomial-time programs). So the result is quite general, since most practical programs are in P. For an introduction to complexity theory, see Arora, Barak (2009) (Draft available here https://theory.cs.princeton.edu/complexity/book.pdf https://theory.cs.princeton.edu/complexity/book.pdf ); same Barak that did the presentation "On the (Im)Possibility of Obfuscating Programs" (2001) mentioned in the abstract.