I know that the translation of "anonymous" is anōnymus. However, it's a bit unclear which suffix to augment this with. I'm trying to determine the phrase "Privacy in anonymity" in Latin.
There are a couple of suffices to use in cases like this. The most common and productive one seems to be -itas, so I would suggest anonymitas (feminine, third declension).
Sometimes also the substantivized neuter can work well. Lewis Elementary suggests that this works for "privacy". Therefore I would translate "privacy in anonymity" directly as privatum in anonymitate.
The direct translation might not be the best one; it depends on what you want to say exactly. Perhaps anonymitas privata or res privata per anonymitatem might be better. It is hard to translate slogans without context.