Although public-key infrastructure (PKI) technology is very useful security technology to realize many security functions (encipherment, digital signature, data integrity, and so on) in the mobile end-to-end data communications, the PKI technology should be adapted for mobile end-to-end data communication. However, the method to construct and manage secure mobile systems based on PKI technology has not been established yet. This Recommendationprovidesguidelines for constructing secure mobile systems based on PKI technology.