Tell People What You Did
One approach to credit is simply to Tell People What You Did. When it matters, citation can be usually sourced and demonstrated.
This is the way most things work in life. When presenting the work of a group in your organization, the ideas aren't tagged according to who originated them, and the report you pass out doesn't specify who did the spreadsheet and who came up with the tagline.
Instead, the work is attributed to the group, and you are (hopefully) empowered to Tell People What You Did (specifically) at times when getting the credit would help you -- talking to your boss, writing up yoour yearly review, applying for a job, getting drinks with colleagues.
There are issues with this approach, however. Many speakers and writers have had the problem that an idea they have been presenting for years suddenly becomes associated with someone else. How to present that idea now without being accused of plagiarism, and without getting into a very defensive "yes this is really my idea" discussion?