This question is a bit unclear.
It is important to understand that non-repudiation is a complex subject that involves legal, social, and technical considerations. Non-repudiation is not just a matter of algorithms. You seem to think that use of public-key cryptography is sufficient for non-repudiation; this is far from the truth.
I suggest you read up on non-repudiation; the concept is much more complex than this question seems to appreciate. In particular, there is not sufficient information here to determine whether the system you have in mind achieves non-repudiation to a reasonable degree.
Here are some readings on non-repudiation: