  Currently, PQC algorithms are being standardized to address the emerging
threat to conventional asymmetric algorithms from quantum computing. These new
algorithms must then be integrated into existing protocols, applications and
infrastructures. Integration problems are to be expected, due to
incompatibilities with existing standards and implementations on the one hand,
but also due to a lack of knowledge among software developers about how to
handle PQC algorithms. To illustrate incompatibilities, we integrate two
different PQC algorithms into two different existing software products (the
InboxPager email client for the Android OS and the TLS implementation of the
Bouncy Castle crypto library). Here, we rely on the highly-abstract crypto
library eUCRITE, which hides technical details about the correct usage of
classical and PCQ algorithms and thus prevents some potential implementation
errors.
