olemus
ISO/IEC 11770-1:
usaldatav olem, mis dekrüpteerib
ühe poole genereeritud võtmeid
ja krüpteerib neid teise poole jaoks uuesti
=
entity trusted to decrypt a key that was generated and encrypted by one party and re-encrypt it for another party

piltlikult
https://image.slidesharecdn.com/pkiipics2002-131102040749-phpapp02/95/pki-is-it-worth-something-or-what-6-638.jpg