Anna and Benoît exchange messages using the following coding table for characters:

Moreover, they use as message unit the tetratagrams (blocks of four letters) that they encode as a number in the following

way:

For example, the word "TEST" becomes the number .

They use the Elgamal cryptosystem with public domain .

Anna's public and private keys are .

Benoît's public and private keys are .

Anna receives the message from Benoît. To which four-letter word this message correponds to ?

Your answer will be a four-letter word in capital letters.

Consider the set equipped with the commutative and associative binary operation described in the table below:

If is a not group, your answer will be "no".

If is a group, find the order of the element (in this case your answer will be a number).

Consider the set equipped with the commutative and associative binary operation described in the table below:

If is a not group, your answer will be "no".

If is a group, find the order of the element (in this case your answer will be a number).