diff --git a/CHANGELOG.md b/CHANGELOG.md
index 86df97e12..78c36987e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@ All notable changes to this project will be documented in this file.
 This project uses the changelog in accordance with [keepchangelog](http://keepachangelog.com/). Please use this to write notable changes, which is not the same as git commit log...
 
 ## [unreleased][unreleased]
+- Fixed DESFire D40 secure channel crypto (@nvx)
 - Fixed `hf mfp info` fix signature check on 4b UID cards (@doegox)
 - Automatically set maximum read/write block when using predefined types in `hf_mf_ultimatecard` script (@piotrva)
 - Changed SPI flash detection to calculate the size instead of table lookup, updated spi_flash_decode.py script with more ICs (@ANTodorov)
diff --git a/client/src/mifare/desfirecore.c b/client/src/mifare/desfirecore.c
index 7bf692184..ac44508f2 100644
--- a/client/src/mifare/desfirecore.c
+++ b/client/src/mifare/desfirecore.c
@@ -1222,14 +1222,17 @@ static int DesfireAuthenticateEV1(DesfireContext_t *dctx, DesfireSecureChannel s
 
     // - Encrypt our response
     if (secureChannel == DACd40) {
+        // Original DESFire (MF3ICD40) silicon can only do encryption operations, so all PCD
+        // side operations must be decrypt, even when encrypting when doing D40 compatible
+        // secure channel operations
         memset(IV, 0, DESFIRE_MAX_CRYPTO_BLOCK_SIZE);
-        DesfireCryptoEncDecEx(dctx, DCOMainKey, RndA, rndlen, encRndA, true, true, IV);
+        DesfireCryptoEncDecEx(dctx, DCOMainKey, RndA, rndlen, encRndA, true, false, IV);
 
         memcpy(both, encRndA, rndlen);
         bin_xor(rotRndB, encRndA, rndlen);
 
         memset(IV, 0, DESFIRE_MAX_CRYPTO_BLOCK_SIZE);
-        DesfireCryptoEncDecEx(dctx, DCOMainKey, rotRndB, rndlen, encRndB, true, true, IV);
+        DesfireCryptoEncDecEx(dctx, DCOMainKey, rotRndB, rndlen, encRndB, true, false, IV);
 
         memcpy(both + rndlen, encRndB, rndlen);
     } else if (secureChannel == DACEV1) {
diff --git a/client/src/mifare/desfiresecurechan.c b/client/src/mifare/desfiresecurechan.c
index d35833b4d..85e2d7d94 100644
--- a/client/src/mifare/desfiresecurechan.c
+++ b/client/src/mifare/desfiresecurechan.c
@@ -313,6 +313,10 @@ static void DesfireSecureChannelEncodeD40(DesfireContext_t *ctx, uint8_t cmd, ui
         size_t srcmaclen = padded_data_length(srcdatalen - hdrlen, desfire_get_key_block_length(ctx->keyType));
 
         uint8_t mac[32] = {0};
+        PrintAndLogEx(DEBUG, "MACing");
+        // Even though original DESFire (MF3ICD40) silicon can only encrypt which means normally
+        // every PCD operation must be decrypt, verifying a MAC involves the same operation on both
+        // sides so this is still encrypt here
         DesfireCryptoEncDecEx(ctx, DCOSessionKeyMac, data, srcmaclen, NULL, true, true, mac);
 
         if (DesfireEV1D40TransmitMAC(ctx, cmd)) {
@@ -889,4 +893,3 @@ bool PrintChannelModeWarning(uint8_t cmd, DesfireSecureChannel secureChannel, De
 
     return found;
 }
-