/usr/include/linbox/blackbox/ is in liblinbox-dev 1.4.2-5build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/linbox/blackbox/apply.h
/usr/include/linbox/blackbox/archetype.h
/usr/include/linbox/blackbox/bb.h
/usr/include/linbox/blackbox/blackbox-interface.h
/usr/include/linbox/blackbox/blackbox.h
/usr/include/linbox/blackbox/block-hankel-inverse.h
/usr/include/linbox/blackbox/block-hankel.h
/usr/include/linbox/blackbox/block-toeplitz.h
/usr/include/linbox/blackbox/butterfly.h
/usr/include/linbox/blackbox/butterfly.inl
/usr/include/linbox/blackbox/companion.h
/usr/include/linbox/blackbox/compose.h
/usr/include/linbox/blackbox/csf.h
/usr/include/linbox/blackbox/csf.inl
/usr/include/linbox/blackbox/diagonal-gf2.h
/usr/include/linbox/blackbox/diagonal.h
/usr/include/linbox/blackbox/dif.h
/usr/include/linbox/blackbox/direct-sum.h
/usr/include/linbox/blackbox/factory.h
/usr/include/linbox/blackbox/fibb.h
/usr/include/linbox/blackbox/frobenius.h
/usr/include/linbox/blackbox/hilbert.h
/usr/include/linbox/blackbox/inverse.h
/usr/include/linbox/blackbox/jit-matrix.h
/usr/include/linbox/blackbox/lambda-sparse.h
/usr/include/linbox/blackbox/matrix-blackbox.h
/usr/include/linbox/blackbox/moore-penrose.h
/usr/include/linbox/blackbox/ntl-hankel.h
/usr/include/linbox/blackbox/ntl-hankel.inl
/usr/include/linbox/blackbox/ntl-sylvester.h
/usr/include/linbox/blackbox/ntl-sylvester.inl
/usr/include/linbox/blackbox/null-matrix.h
/usr/include/linbox/blackbox/pascal.h
/usr/include/linbox/blackbox/permutation.h
/usr/include/linbox/blackbox/polynomial.h
/usr/include/linbox/blackbox/quad-matrix.h
/usr/include/linbox/blackbox/random-matrix-traits.h
/usr/include/linbox/blackbox/random-matrix.h
/usr/include/linbox/blackbox/rational-matrix-factory.h
/usr/include/linbox/blackbox/scalar-matrix.h
/usr/include/linbox/blackbox/scompose.h
/usr/include/linbox/blackbox/squarize.h
/usr/include/linbox/blackbox/submatrix-traits.h
/usr/include/linbox/blackbox/submatrix.h
/usr/include/linbox/blackbox/sum.h
/usr/include/linbox/blackbox/toeplitz.h
/usr/include/linbox/blackbox/toeplitz.inl
/usr/include/linbox/blackbox/transpose.h
/usr/include/linbox/blackbox/zero-one.h
/usr/include/linbox/blackbox/zero-one.inl
/usr/include/linbox/blackbox/zo-gf2.h
/usr/include/linbox/blackbox/zo-gf2.inl
/usr/include/linbox/blackbox/zo.h
/usr/include/linbox/blackbox/zo.inl