Enhanced security in sensitive data transfer over a network

A computer-implemented method for authenticating a transaction over a secure network, the method comprising:

• prior to authorization of a transaction:
• receiving, by a digital service server, from a merchant plug-in (MPI) computing device, via a directory server, a token and a first cryptogram for the transaction, the first cryptogram unique to the transaction;
• and then decrypting, by the digital service server, the token into sensitive data;
• diversifying, by the digital service server, a master key from an issuer master symmetric key, which is specific to an issuer;
• diversifying, by the digital service server, one or more session keys from the diversified master key based on an application transaction count (ATC);
• validating, by the digital service server, the first cryptogram, based on the one or more diversified session keys;
• and then
• based on the first cryptogram being validated:
• incrementing, by the digital service server, the ATC;
• and
• generating, by the digital service server, a first message including a validation result and the sensitive data;
• and then
• transmitting, by the digital service server, the first message to an issuer server of the issuer to authenticate the transaction.