You want to get into a secret clubhouse. Normally the clubhouse has a secret phrase that you say before they open the door.

e.g.

"Knock Knock"
"Who's there?"
"Amar"
"What's the secret word?"
"Swordfish"
"Come on in Amar"

But now there is a different way of getting into the clubhouse! It has two parts - a magic encoder machine that you have and magic decoder glasses the clubhouse has. This magic encoder machine is private and very secret. It makes two things - magic decoder glasses and pieces of paper with writing that only the magic decoder glasses can read.

You give the clubhouse magic decoder glasses. They will let you in if you give them a paper the magic encoder machine made. They can tell the magic encoder machine made the paper because they can read it with the magic decoder glasses.

Now getting in the clubhouse is like this:

"Knock Knock"
"Who's there?"
"Amar, and here's my secret paper"
\Club door-person puts on Amar's magic glasses and reads the paper
"Come on in Amar"