diff --git a/src/SD.cpp b/src/SD.cpp
index 423db45..a952a63 100644
--- a/src/SD.cpp
+++ b/src/SD.cpp
@@ -371,6 +371,18 @@ namespace SDLib {
     root.close();
   }
 
+  // protect a card with a password or remove it
+  bool SDClass::lockCard(bool setLock, const char pwd) {
+    return card.lockCard(setLock, pwd);
+  }
+  
+  // !!CAUTION!! call this to completely erase a card,
+  // this will unlock a card but also delete the complete file system,
+  // reformatting will be required!
+  bool SDClass::forceEraseCard(){
+    return card.forceEraseCard();
+  }
+
   // this little helper is used to traverse paths
   SdFile SDClass::getParentDir(const char *filepath, int *index) {
     // get parent directory
diff --git a/src/SD.h b/src/SD.h
index c81a7d3..b1011a5 100644
--- a/src/SD.h
+++ b/src/SD.h
@@ -106,6 +106,12 @@ namespace SDLib {
         return rmdir(filepath.c_str());
       }
 
+      // lock card with a password
+      bool lockCard(bool setLock, const char pwd);
+      // !!CAUTION!! this can be used as last resort if the password of a locked card is unknown,
+      // this will remove the files and filesystem, a reformatting of the card is necessary after this
+      bool forceEraseCard();
+
     private:
 
       // This is used to determine the mode used to open a file
diff --git a/src/utility/Sd2Card.cpp b/src/utility/Sd2Card.cpp
index 7cfbe73..6ed26cd 100644
--- a/src/utility/Sd2Card.cpp
+++ b/src/utility/Sd2Card.cpp
@@ -775,3 +775,83 @@ uint8_t Sd2Card::isBusy(void) {
 
   return (b != 0XFF);
 }
+
+/** Locks a card with a password
+  \param[in] setLock true if the card should be locked, false if it should be unlocked
+  \param[in] pwd password to lock/unlock the card
+  
+  \return true if the locking was successful
+*/
+bool Sd2Card::lockCard(bool setLock, const char *pwd){
+  if(!isBusy()){
+    int16_t i;
+    uint8_t pwd_len = sizeof(pwd);
+    bool locked = false;
+
+    if(cardCommand(CMD42, 0) != 0){
+      return false;
+    }
+
+    spiSend(DATA_START_BLOCK);
+    if(setLock) {
+      spiSend(SET_CARD_PWD & 0x07);
+    }
+    else{
+      spiSend(CLEAR_CARD_PWD & 0x07);
+    }
+
+    spiSend(pwd_len);
+    for(i=0; i<512; i++){
+      if(i<pwd_len){
+        spiSend(pwd[i]);
+      }
+      else{
+        spiSend(0xFF);
+      }
+    }
+
+    locked = getCardStatus();
+      
+    spiSend(0xFF);
+    spiSend(0xFF);
+
+    i = 0xFFFF;
+    while(isBusy() && (--i));
+
+    return locked;
+  }
+}
+
+/** Completely erase a card
+  !! Use with caution !! this removes everything from a card, even the file system.
+  Use this to remove a lock with an unknown password from a card.
+
+  \return true if the erase was successful
+*/
+bool Sd2Card::forceEraseCard(void) {
+  // set block size to 512 bytes
+  cardCommand(CMD16, 1);
+
+  // enable 
+  if(cardCommand(CMD42, 0) != 0){
+    return false;
+  }
+
+  spiSend(DATA_START_BLOCK);
+  spiSend(FORCE_ERASE);
+
+  return true;
+}
+
+/** Check status of card lock
+  \return true if card is locked
+*/
+bool Sd2Card::getCardStatus(void) {
+  bool cardOK = true;
+
+  if(cardCommand(CMD13, 0) || spiRec()) {
+    cardOK = false;
+  }
+
+  return cardOK;
+}
diff --git a/src/utility/Sd2Card.h b/src/utility/Sd2Card.h
index 5d91ebf..f5df3e2 100644
--- a/src/utility/Sd2Card.h
+++ b/src/utility/Sd2Card.h
@@ -241,6 +241,9 @@ class Sd2Card {
     uint8_t writeStart(uint32_t blockNumber, uint32_t eraseCount);
     uint8_t writeStop(void);
     uint8_t isBusy(void);
+    bool lockCard(bool setLock, const char *pwd);
+    bool forceEraseCard(void);
+    bool getCardStatus(void);
   private:
     uint32_t block_;
     uint8_t chipSelectPin_;
diff --git a/src/utility/SdInfo.h b/src/utility/SdInfo.h
index 6a0e087..e63e737 100644
--- a/src/utility/SdInfo.h
+++ b/src/utility/SdInfo.h
@@ -42,6 +42,8 @@ uint8_t const CMD9 = 0X09;
 uint8_t const CMD10 = 0X0A;
 /** SEND_STATUS - read the card status register */
 uint8_t const CMD13 = 0X0D;
+/** SET_BLOCKLEN - change r/w block size */
+uint8_t const CMD16 = 0X10;
 /** READ_BLOCK - read a single data block from the card */
 uint8_t const CMD17 = 0X11;
 /** WRITE_BLOCK - write a single data block to the card */
@@ -55,6 +57,8 @@ uint8_t const CMD32 = 0X20;
 uint8_t const CMD33 = 0X21;
 /** ERASE - erase all previously selected blocks */
 uint8_t const CMD38 = 0X26;
+/** LOCK_CMD - lock card with password */
+uint8_t const CMD42 = 0x2A; 
 /** APP_CMD - escape for application specific command */
 uint8_t const CMD55 = 0X37;
 /** READ_OCR - read the OCR register of a card */
@@ -82,6 +86,14 @@ uint8_t const WRITE_MULTIPLE_TOKEN = 0XFC;
 uint8_t const DATA_RES_MASK = 0X1F;
 /** write data accepted token */
 uint8_t const DATA_RES_ACCEPTED = 0X05;
+/** mask for setting a card password*/
+uint8_t const SET_CARD_PWD = 0x01;
+/** mask for removing a card password*/
+uint8_t const CLEAR_CARD_PWD = 0x02;
+/** mask for locking or unlocking a card*/
+uint8_t const ACTIVATE_CARD_LOCK = 0x04;
+/** mask to erase the entire card*/
+uint8_t const FORCE_ERASE = 0x08;
 //------------------------------------------------------------------------------
 typedef struct CID {
   // byte 0