The (in)security of proprietary cryptography

Proprietary cryptography is a term used to describe custom encryption techniques that are kept secret by its designers to add additional security. It is questionable if such an approach increases the cryptographic strength of the underlying mathematical algorithms. The security of proprietary encryption techniques relies entirely on the competence of the semi - conductor companies, which keep the technical description strictly confidential after designing. It is difficult to give a public and independent security assessment of the cryptography, without having access to the detailed information of the design. The first part of this dissertation is dedicated to an introduction of the general field of computer security and cryptography. It includes an extensive description of the theoretical background that refers to related literature and gives a summary of well - known cryptographic at tack techniques. Additionally, a broad summary of related scientific research on proprietary cryptography is given. Finally, the technical part of this doctoral dissertation presents serious weaknesses in widely deployed proprietary cryptosystems, which are still actively used by billions of consumers in their daily lives.