A transaction system is provided for a merchant and a consumer to conduct a point-of-sale (POS) transaction. The transaction system includes a host, a consumer transaction processor, and a merchant transaction processor. The host provides a merchant authorization key and a consumer authorization key which co-operates as a pair with the merchant authorization key. The consumer transaction server receives the consumer authorization key from the host, and communicates the consumer authorization key to a portable wireless client of the consumer to allow the consumer to send the consumer authorization key to a POS terminal of the merchant. The merchant transaction server receives the merchant authorization key from the host, and compares the merchant authorization key with the consumer authorization key when the consumer authorization key is received from the POS terminal of the merchant. A message is sent to the POS terminal of the merchant to indicate a successful transaction if the comparison of the keys reveals that the keys comprise a pair. As an example, the keys comprise a pair when the keys match. A message is sent to the POS terminal of the merchant to indicate a failed transaction if the comparison of the keys reveals that the keys do not comprise a pair.