As penetration testers, it's not uncommon to find applications where developers make custom implementations of standard encryption protocols or attempt to create their own custom algorithms. In such cases, you need to pay special attention to these modules, as they may contain several flaws that could prove catastrophic if released into production environments.
As stated previously, encryption algorithms are created by information security experts and mathematicians specialized in cryptography through years of experimentation and testing. It is highly improbable for a single developer or small team to design a cryptographically strong algorithm or to improve on an intensively tested implementation such as OpenSSL or the established cryptographic libraries of programming languages.
