The KSD-64[A] Crypto Ignition Key (CIK) is an NSA-developed EEPROM chip packed in a plastic case that looks like a toy key. The model number is due to its storage capacity — 64 kilo bits (65,536 bits), enough to store multiple encryption keys. Most frequently it was used in key-splitting applications: either the encryption device or the KSD-64 alone is worthless, but together they can be used to make encrypted connections. It was also used alone as a fill device for transfer of key material, as for the initial seed key loading of an STU-III secure phone.