A method comprising: generating (S1), by a mobile communication device, a first cryptogram using a first identifier and a first cryptographic key, stored in a memory of the mobile communication device using a first cryptographic protocol; generating (S2), within a key store of the mobile communication device, a second cryptogram using a second identifier and a second cryptographic key that is stored in the key store using a second cryptographic protocol that is different from the first cryptographic protocol; generating a third cryptogram by combining (S3), by the mobile communication device, the first cryptogram and a number of characters of the second cryptogram equal to a length of the first cryptogram, comprising applying a reversible logical operation to the first cryptogram and the number of characters of the second cryptogram; transmitting (S4), by the mobile communication device, the third cryptogram in an authorization request message to a payment processing computer; receiving, by a computing device of the payment processing computer that has access to a stored copy of the second cryptogram or the ability to recreate the second cryptogram using a stored version of the second cryptographic key and the second identifier, the authorization request message including the third cryptogram; obtaining or recreating, by the payment processing computer, the second cryptogram; producing (S5), by the payment processing computer, the first cryptogram by applying the second cryptogram to the third cryptogram received in the authorization request message, thereby reversing the logical operation; transmitting (S6), by the payment processing computer, an updated authorization request message including the first cryptogram to an issuer computer. generating (S1), by a mobile communication device, a first cryptogram using a first identifier and a first cryptographic key, stored in a memory of the mobile communication device using a first cryptographic protocol; generating (S2), within a key store of the mobile communication device, a second cryptogram using a second identifier and a second cryptographic key that is stored in the key store using a second cryptographic protocol that is different from the first cryptographic protocol; generating a third cryptogram by combining (S3), by the mobile communication device, the first cryptogram and a number of characters of the second cryptogram equal to a length of the first cryptogram, comprising applying a reversible logical operation to the first cryptogram and the number of characters of the second cryptogram; transmitting (S4), by the mobile communication device, the third cryptogram in an authorization request message to a payment processing computer; receiving, by a computing device of the payment processing computer that has access to a stored copy of the second cryptogram or the ability to recreate the second cryptogram using a stored version of the second cryptographic key and the second identifier, the authorization request message including the third cryptogram; obtaining or recreating, by the payment processing computer, the second cryptogram; producing (S5), by the payment processing computer, the first cryptogram by applying the second cryptogram to the third cryptogram received in the authorization request message, thereby reversing the logical operation; transmitting (S6), by the payment processing computer, an updated authorization request message including the first cryptogram to an issuer computer. <EOS>