4.1 Use strong cryptography and security protocols (for example, SSL/TLS, IPSEC, SSH, etc.) to safeguard sensitive cardholder data during transmission over open, public networks.
Examples of open, public networks that are in scope of the PCI DSS include but are not limited to:
The Internet
Wireless technologies,
Global System for Mobile communications (GSM)
General Packet Radio Service (GPRS).