VALIDATION OF GRID MODEL INTEGRITY FROM THE INFORMATION SECURITY ASPECT The CIA (Confidentiality, Integrity, Availability) triad is a guiding model used to find vulnerabilities and methods to minimize threats related to information security. In the case of operational planning of the Electrical Power and Energy System (EPES), the key datasets are Individual Grid Models (IGMs) and Common Grid Models (CGMs), since data contained in these grid models is used to forecast expected EPES behavior in the future. Many different control measures have been implemented within the ENTSO-E community to protect the confidentiality and availability of the mentioned grid models, while the integrity of these models was not so much the focus.As part of the R²D² (Reliability, Resilience and Defense technology for the griD) project, funded through the Horizon Europe program, the KSI (Keyless Signature Infrastructure) system was implemented to validate the integrity of IGMs and CGMs. Using specific blockchain technology, the KSI system is in a position to process these grid models and create a signature file, which represents a proof of data integrity.The paper describes general concepts related to the KSI system and KSI blockchain technology, how the integrity of data could be proved, and how the KSI system is implemented in the CGM building process.