If the security infrastructure (PKI) takes place via mobile devices
, it is referred to as mobile PKI (mPKI). The functionality of mPKI differs in that with mobile Public KeyInfrastructure (PKI) the user does not encrypt and digitally sign contracts, purchase orders or confirmations of receipt via his stationary computer, but via mobile phone. In mobile PKI, the smartphone works as a low-cost card reader. In addition, the SIM card could hold sensitive encryption data.