A tamper-evident data management system uses public-private digital signature keys to control use of data and to ensure the fidelity of data that is stored on a customer's system for later collection by a computer vendor or that is sent to the vendor over a network. A computer system includes an application for collecting usage or metrics data from the computer system, for example. The metering application uses an application private key to digitally sign all metrics data prior to optionally storing the data in a data log file. The vendor can then use an application public key to validate the digitally signed entries. The digitally signed data entries may also be encrypted using a vendor public key prior to storage in the data log and may be decrypted using a vendor private key prior to validating the digitally signed data. The application and application private key may be stored on a smart card to discourage and detect tampering or may be stored on the computer system itself.