Signed proof of data integrity checks for events, logs and API results. Source authentication of a registered app; freshness checks. Tamper-evident receipts; offline verification with trusted key and original data. No proof of real-world events. EUR10 net+VAT; EU B2B; non-monetary events or EUR100-300 transactions. https://api.integrityphase.com/.well-known/integrityphase-commerce.json