Description:

The term 'ki' is thought to come from English, possibly via cryptography. In modern High Common it confusingly means both key and lock when referring to physical systems. It has a precise technical meaning in computer science as a cryptographic key but also a more general sense in casual language to refer to encryption in general. 

Noun:

In a noun context, ki refers to a physical key or lock.

The derived form 'kisyn' usually refers to encryption but can also generally refer to physical security. It means security in the sense of being safe from intrusion or theft, or snooping, and it can also mean security in the sense of prevention from escape.

The derived form 'kiwala' refers to a security device such as a padlock, although it can again still confusingly refer to a physical key.

Modifier:

The modifier form 'kis' means something like, 'locked up' or 'secure'. The form 'kikas' is about the same but refers specifically to something that has been secured.

Verb:

In a verb context, 'ki' is a transitive skurun verb meaning something like 'to lock (up)' or 'to secure'. E.g.:

Je tene ki a felo.

I locked up my bike.