https://www.by4si.com/ 2026-07-19 https://www.by4si.com/assets/editorial/4si-key-verification.webp 4SI physical verification for human authorization A Presence Key being presented for physical verification. https://www.by4si.com/presence 2026-07-19 https://www.by4si.com/assets/product-studies/key-system.jpg Presence Key physical trust system Presence Key and its controlled verification system. https://www.by4si.com/applications 2026-07-19 https://www.by4si.com/assets/editorial/product-authenticity.webp Physical product authenticity verification Physical verification supporting product authenticity and chain of custody. https://www.by4si.com/company 2026-07-19 https://www.by4si.com/assets/founder/niclas-braun-study.jpg Niclas Braun, founder of 4SI https://www.by4si.com/company/niclas-braun 2026-07-19 https://www.by4si.com/assets/founder/niclas-braun-study.jpg Niclas Braun, founder and CEO of 4SI Niclas Braun, German deep-tech entrepreneur and founder and CEO of 4SI. https://www.by4si.com/papers2026-07-19 https://www.by4si.com/verification-control-primitive2026-07-19 https://www.by4si.com/economic-research 2026-07-19 https://www.by4si.com/assets/editorial/natural-delta-signature.webp The economics of verifiable reality A branching natural system illustrating physical origin and distributed pathways. https://www.by4si.com/approach2026-07-19 https://www.by4si.com/faq2026-07-19 https://www.by4si.com/glossary2026-07-19 https://www.by4si.com/careers2026-07-19 https://www.by4si.com/contact2026-07-19 https://www.by4si.com/access2026-07-19 https://www.by4si.com/responsible-disclosure2026-07-19 https://www.by4si.com/privacy2026-07-19 https://www.by4si.com/cookies2026-07-19 https://www.by4si.com/terms2026-07-19