Nonrepudiation w/ symmetric crypto

nuglobe

On the Sybex flashcards it asks:

"Can nonrepudiation be achieved using symmetric/private keys?"

The answer is no, but I dont see why that is.

Can someone help me out.

Thanks.

seuss_ssues

Sym keys arent used for authentication or nonrepudiation.

With Sym (private) key encryption the sender and receiver have the same key. Therefore if something were encrypted there is no way to determine who encrypted it so there isnt the ability to have nonrepudiation.