Each team has a screen of four random words, that are numbered 1-4, positioned in a way such that everyone on the same team can see these words, whilst the words remain hidden from the other team. In the first round, each team does the following: The "Transmitter" takes a code card that shows three of the digits 1-4 in some order, e.g., 3-4-1. They then give clues that correspond to the words in sequential order such that the teammates can guess this code. E.g. If the white team's words are "Cat", "Beer", "Train", "Sing", then the transmitter might give a clue like "Transport", "Adele", "Dog" and hope that the teammates can correctly map to 3-4-1. The team does not get rewarded for guessing their own code correctly but will get penalised a miscommunication token for guessing it wrong.
HOWEVER: The opposing team is also writing down all these clues, and the correct codes. Before you can guess your own code, the opposing team has a chance to guess before you do. If they guess correctly they get a Decrypto'ed token.
Giving clues suddenly became a lot trickier because being too obvious increases the other team's chances of guessing. The rounds continue until a team collects either its second Decrypto'ed token (and they win), or its second miscommunication token (and they lose, and the other team wins). Games typically last between 4-7 rounds. If neither team has won after eight rounds, then each team must attempt to guess the other team's words; whichever team guesses more words correctly wins.