The MIFARE DESFire EV1 4K card from NXP operates at 13.56 MHz wireless frequency, according to the ISO 14443A standard with the transport protocol complying to the ISO 14443-4 standard. It features a 4K byte non volatile memory, a high speed triple-DES data encryption co-processor, a flexible memory organization structure, a mutual 3-pass authentication technique together with a true random number generator and an anti-tear mechanism to guarantee data integrity during contactless transactions.

These are the 4K version of the chips used in the FlexDF