Invariant subspace attacks were introduced at CRYPTO 2011 to cryptanalyze PRINTcipher. The invariant subspaces for PRINTcipher were discovered in an ad hoc fashion, leaving a generic technique to discover invariant subspaces in other ciphers as an open problem. Here, based on a rather simple observation, we introduce a generic algorithm to detect invariant subspaces. We apply this algorithm to ...

For a Veech surface (X, ω), we characterize Aff + (X, ω) invariant subspaces of X n and prove that non-arithmetic Veech surfaces have only finitely many invariant subspaces of very particular shape (in any dimension). Among other consequences we find copies of (X, ω) embedded in the moduli-space of translation surfaces. We study illumination problems in (pre-)lattice surfaces. For (X, ω) prelat...