Certain applications of passive radio frequency identification (RFID), such as those in healthcare where the patient’s name, identification or medical record must be stored, require data within a tag to be encrypted. Encrypted data within an RFID tag has the potential to affect the accuracy or time to read/write the data by the reader. The current research measures and analyzes the effects of encryption, distance of read and delay time between two read/write cycles on the accuracy of the read or write function in an RFID infrastructure. The research also measures and evaluates the time to read/write (R/W) data that is encrypted and compares this encrypted data with unencrypted data. The data encryption standard (DES) encryption method is used in this research due to the limitation of the tag. A multi-functional interface has been developed for the user to test the performance using a High Frequency RFID reader. The measurements were repeated 1000 times for each R/W test. The performance of R/W accuracy is not affected in any meaningful way by encryption even though there is an increase in memory requirement from 88 bytes to 128 bytes. The effect of R/W distance shows that the performance decreases with increase in the distance between the reader and the tag. By inserting a small amount of delay time between different cycles, we can get a significant increase up to 100% accuracy for read function. However, the write accuracy is not affected as significantly as the read accuracy. The effect of the encryption on the time to write the data on the tag shows that encrypted data group takes 70 - 120 milliseconds for the transmission more than the unencrypted data group. We conclude that while the encryption does not have a significant impact on the accuracy of R/W, the distance and cycle delay does. Also, the encrypted data takes longer to write to the tag.