Simplify the following text for a Grade 12 native English-speaking person.
Original: Kerberos builds on symmetric key cryptography and requires a trusted third party , and optionally may use public-key cryptography by utilizing asymmetric key cryptography during certain phases of authentication .
Simplified: Kerberos builds on symmetric-key cryptography and requires a key distribution center . Extensions to Kerberos can provide for the use of public-key cryptography during certain phases of authentication .