It's only a crime if they ask you and you mislead them.

If asked, you can refuse to talk based on the fifth amendment/Miranda, but you can't lie.

You are also not required to come forth without being asked and spill your guts just because of something you read on the internet. In certain cases (some federal felonies, some state crimes) you may be legally obligated to report the fact that a crime occurred, but they already know that in this case