This article gives a historical overview of the various design criteria of the Data Encryption Standard (DES) and some of its variants, starting from the legendary conditions given by Coppersmith in 1994. The authors follow their development until now, as simplified DES-like ciphers exist with improved properties. While doing so, they analyze the properties imposed on the S-boxes and the permutation used in the round function, and explain implications on the resistance of these ciphers against differential and linear cryptanalysis.

Advances in quantum computing necessitate migrating the entire technology stack to post-quantum cryptography. This includes IPsec-based VPN connection authentication. Although there is an RFC draft for post-quantum authentication in this setting, the draft does not consider (stateful) hash-based signatures despite their small signature size and trusted long-term security. We propose a design with time-based state-management that assigns VPN devices a certificate authority (CA) based on the hash-based signature scheme XMSS. The CA then issues leaf certificates which are based on classical cryptography but have a short validity time, e. g., four hours. It is to be expected that even large quantum computers will take significantly longer to break the cryptography, making the design quantum-secure. We propose strategies to make the timekeeping more resilient to faults and tampering, as well as strategies to recognize a wrong system time, minimize its potential damage, and quickly recover. The result is an OpenBSD implementation of a quantum-safe and, regarding the leaf certificates, highly flexible VPN authentication design that requires significantly less bandwidth and computational resources compared to existing alternatives.

Creators of digital artifacts are increasingly competing with generative artificial intelligence. Next to common plagiarism, this is another reason why proving one’s authorship becomes increasingly important. One way to support this proof is to document the work process in a certified artifact. Blockchain technology lends itself to this by generation of a data structure that is intrinsically unchangeable and via strong asymmetric cryptographic algorithms tied to the creator. In this paper, we present a concept to record and validate one’s creative work. To demonstrate its feasibility, we provide a proof of concept implementation that documents and encodes a sculpting process conducted in the open-source modeling software Blender.