How to properly claim credit for peer review? I acted as a reviewer for a paper this year and would like to mention this in my CV. However, I would like the authors not to know that I was the reviewer before some time.

At the moment, I have remained intentionally vague in my CV, mentioning only the journal name and the topic of the article. Is there a way to do better, namely:


Is it possible to make this review work verifiable? (perhaps by giving the email of the editor?)
Is it ethical to point to the full published paper in a CV that I don’t intend to distribute widely?
The standard information to give is the journal's name and only this. As far as I recall I have never seen a CV that gives more details than that (mostly I know academic CVs of mathematicians).  

I would not go as far as saying that it would be unethical to include more information, but it would seem unusual and the advantage is not very clear. 

If you are concerned about the claim not being credible, I'd not worry too much about this. However, some journals and publishers offer certificates for reviewers. See for example this information about reviewer recognition at Elsevier 

There may be exceptions to this if you happen to be involved in some very high profile reviewing endeavor, but if you reviewed a normal paper I'd just give the journal's name.