Abstract: QSecure Validation Service (QVS™) is part of the QSecure Suite and includes a CVQ Table Generator (QTG) for use with a QBox™ card personalizer. In general, the QVS/QVM compares dynamic CVQ token data fetched by an issuer authorization host from a transaction then occurring in the field. An array of acceptable CVQ values computed in real-time from the original keys and algorithms used by the QTG and QBox to personalize the particular card are applied in the comparison. There is an order to the CVQ values in such array, and the dynamic CVQ token data will step through these over time. Small deviations in the order actually received can normally occur for reasons other than fraud, so a moving window of acceptance is needed to cope with normal deviations. A running account of which CVQ values have already been used is maintained for, or by, the QVS, and these help predict where the acceptance window should next be positioned in the array of acceptable CVQ values.