We propose an efficient and flexible system for a secure and authentic data exchange in a multi-institutional environment, where the institutions maintain different databases and provide secure and limited access services to employees of other institutions. The main motivation for building such a system was to organize efficient cooperative use of state registers, in order to increase the efficiency and quality of public services in Estonia. In order to meet high security requirements, several contemporary measures are integrated (using digital signatures, distributing certificate information by means of DNS protocol and linking log files with crypto-graphic checksums). We give rationale for the design decisions made in the implementation process and conclude with the current state of public use of the resulting infrastructure.