Classic operation). This does not prevent the attacks mentioned above but enables a secure mutual authentication between the reader and the card to prove that the card belongs to the system and is not fake. In its highest security level SL3, using 128-bit AES encryption, MIFARE Plus is secured from attacks. MIFARE Plus EV1 MIFARE Plus EV1 was announced in April 2016. New features compared to MIFARE Plus X include: Sector-wise security-level switching The choice of crypto algorithm used in the authentication protocol can be set separately for each sector. This makes it possible to use the same card with both readers that can read MIFARE Classic products (with sectors protected by 48-bit CRYPTO1 keys, "Security Level 1") and readers that can read MIFARE Plus products (with sectors protected by 128-bit AES keys, "Security Level 3"). This feature is intended to make it easier to gradually migrate existing MIFARE Classic product-based installations to MIFARE Plus, without having to replace all readers at the same time. ISO 7816-4 wrapping The card can now be accessed in either the protocol for MIFARE (which is not compliant with the ISO 7816-4 APDU format), or using a new protocol variant that runs on top of ISO 7816-4. This way the cards become compatible with NFC reader APIs that can only exchange messages in ISO 7816-4 APDU format, with a maximum transfer data buffer size of 256 bytes. Proximity check While the protocol for MIFARE Classic tolerated message delays of several seconds, and was therefore vulnerable to relay attacks, MIFARE Plus EV1 now implements a basic "ISO compliant" distance-bounding protocol. This puts tighter timing constraints on the permitted round-trip delay during authentication, to make it harder to forward messages to far-away cards or readers via computer networks. Secure end-2-end channel Permits AES-protected over-the-air updates even to Crypto1 application sectors (SL1SL3 mix mode). Transaction MAC The card can produce an additional message-authentication code over a transaction that can be verified by a remote clearing service, independent of the keys used by the local reader during the transaction. MIFARE Plus EV2 The MIFARE Plus EV2 was introduced to the market on 23 June 2020. It comes with an enhanced read performance and transaction speed compared to MIFARE Plus EV1. New features compared to MIFARE Plus EV1 include: Transaction Timer To help mitigate man-in-the-middle attacks, the Transaction Timer feature, which is also available on NXP’s MIFARE DESFire EV3