I'm an engineer by formation, with experience in applied cryptography, in particular in Smart Card systems. My current professional activity is in payment of public services (such as transport) with contactless Smart Cards and mobile phones.

About my icon: it's a call to VOTE¹ in political elections. At a vote place, within a voting booth, by inserting paper in an envelope, then the envelope in a transparent ballot box, if at all possible². When you think about it from a cryptographer's perspective, that's the best protocol to decide who governs.

Feel free to edit my answers to fix obvious errors, or improve them on expression (I'm not a native English speaker).

¹ It has been understood as: vote in StackExchange moderator elections. I support that too.

² If your local voting rules became overly complex, what about back-to-the-basics, and Voter Verified Paper Audit Trail as a least evil?