diff --git a/Firmware/Chameleon-Mini/Application/TITagitstandard.c b/Firmware/Chameleon-Mini/Application/TITagitstandard.c
index 73784fb..f334b99 100644
--- a/Firmware/Chameleon-Mini/Application/TITagitstandard.c
+++ b/Firmware/Chameleon-Mini/Application/TITagitstandard.c
@@ -22,6 +22,9 @@ static enum {
     STATE_QUIET
 } State;
 
+uint16_t UserLockBits_Mask = 0;     /* Holds lock state of blocks */
+uint16_t FactoryLockBits_Mask = 0;  /* Holds lock state of blocks */
+
 //ISO15693UidType Uid = {0x00, 0x00, 0x00, 0x00, 0x00, 0xC0, 0x07, 0xE0};
 //0xE0 = iso15693
 //0x07 = TEXAS INSTRUMENTS
@@ -30,6 +33,9 @@ static enum {
 void TITagitstandardAppInit(void)
 {
     State = STATE_READY;
+    FactoryLockBits_Mask |= (1 << 8);   /* Locks block 8... */
+    FactoryLockBits_Mask |= (1 << 9);   /* ...and 9, which contains the UID */
+    UserLockBits_Mask |= (1 << 3);   /* TESTING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! */
 }
 
 void TITagitstandardAppReset(void)
@@ -92,19 +98,24 @@ uint16_t TITagitstandardAppProcess(uint8_t* FrameBuf, uint16_t FrameBytes)
 					}
 
                     if (FrameBuf[ISO15693_ADDR_FLAGS] & ISO15693_REQ_FLAG_OPTION) { /* request with option flag set */
-                        FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR;
-                        /* UID is stored in blocks 8 and 9 which are blocked */
-                        FrameBuf[1] = ( PageAddress == 8 || PageAddress == 9) ? 0x02 : 0x00; /* block security status: when request has the option flag set */
+                        if (FactoryLockBits_Mask & (1 << PageAddress)) { /* tests if the n-th bit of the factory bitmask if set to 1 */
+                            FrameBuf[1] = 0x02; /* return bit 1 set as 1 (factory locked) */
+                        }
+                        else if (UserLockBits_Mask & (1 << PageAddress)) { /* tests if the n-th bit of the user bitmask if set to 1 */
+                            FrameBuf[1] = 0x01; /* return bit 0 set as 1 (user locked) */
+                        }
+                        else
+                            FrameBuf[1] = 0x00; /* return lock status 00 (unlocked) */
 			            FramePtr = FrameBuf + 2;
                         ResponseByteCount = 6;
-                    } else { /* request with option flag not set*/
-                        FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR; /* Flags */
+                    } else { /* request with option flag not set */
 			            FramePtr = FrameBuf + 1;
                         ResponseByteCount = 5;
                     }
 
-		            MemoryReadBlock(FramePtr, PageAddress * TITAGIT_BYTES_PER_PAGE, TITAGIT_BYTES_PER_PAGE);
+                    FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR; /* flags */
 
+		            MemoryReadBlock(FramePtr, PageAddress * TITAGIT_BYTES_PER_PAGE, TITAGIT_BYTES_PER_PAGE);
                 }
 
             	else if (Command == ISO15693_CMD_WRITE_SINGLE) {
@@ -112,6 +123,8 @@ uint16_t TITagitstandardAppProcess(uint8_t* FrameBuf, uint16_t FrameBytes)
 					uint8_t PageAddress;
 
                     if (ISO15693Addressed(FrameBuf)) {
+                        if (FrameBytes < (0x01 + 0x01 + 0x08 + 0x01 + 0x04)) /* flag + cmd + uid + block number + data */
+                            break; /* malformed: not enough data */
                         if (ISO15693CompareUid(&FrameBuf[ISO15693_REQ_ADDR_PARAM], Uid)) {/* write is addressed to us */
                             /* pick block 2 + 8 (UID Lenght) */
                             PageAddress = FrameBuf[ISO15693_REQ_ADDR_PARAM + 0x08]; /*when receiving an addressed request pick block number from 10th byte in the request*/
@@ -121,17 +134,57 @@ uint16_t TITagitstandardAppProcess(uint8_t* FrameBuf, uint16_t FrameBytes)
                         else /* we are not the addressee of the write command */
                             break;
 		            } else { /* request is not addressed */
+                        if (FrameBytes < (0x01 + 0x01 + 0x01 + 0x04)) /* flag + cmd + block number + data */
+                            break; /* malformed: not enough data */
 			            PageAddress = FrameBuf[ISO15693_REQ_ADDR_PARAM];
                         Dataptr = &FrameBuf[ISO15693_REQ_ADDR_PARAM + 0x01];
                     }
 
-					MemoryWriteBlock(Dataptr, PageAddress * TITAGIT_BYTES_PER_PAGE, TITAGIT_BYTES_PER_PAGE);
-					FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR;
-					ResponseByteCount = 1;
+                    if (FactoryLockBits_Mask & (1 << PageAddress)) {
+                        FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_ERROR;
+                        FrameBuf[ISO15693_ADDR_FLAGS + 1] = ISO15693_RES_ERR_OPT_NOT_SUPP;
+                        ResponseByteCount = 2;
+                    } else if (UserLockBits_Mask & (1 << PageAddress)) {
+                        FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_ERROR;
+                        FrameBuf[ISO15693_ADDR_FLAGS + 1] = ISO15693_RES_ERR_BLK_CHG_LKD;
+                        ResponseByteCount = 2;
+                    } else {
+                        MemoryWriteBlock(Dataptr, PageAddress * TITAGIT_BYTES_PER_PAGE, TITAGIT_BYTES_PER_PAGE);
+                        FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR;
+                        ResponseByteCount = 1;
+                    }
 				}
+
+                else if (Command == ISO15693_CMD_LOCK_BLOCK) {
+                    uint8_t PageAddress;
+                    if (ISO15693Addressed(FrameBuf)) {
+                        if (FrameBytes < (0x01 + 0x01 + 0x08 + 0x01)) /* flag + cmd + uid + block number + data */
+                            break; /* malformed: not enough data */
+                        if (ISO15693CompareUid(&FrameBuf[ISO15693_REQ_ADDR_PARAM], Uid)) {/* write is addressed to us */
+                            /* pick block 2 + 8 (UID Lenght) */
+                            PageAddress = FrameBuf[ISO15693_REQ_ADDR_PARAM + 0x08]; /*when receiving an addressed request pick block number from 10th byte in the request*/
+                        }
+                        else /* we are not the addressee of the write command */
+                            break;
+		            } else { /* request is not addressed */
+                        if (FrameBytes < (0x01 + 0x01 + 0x01)) /* flag + cmd + block number + data */
+                            break; /* malformed: not enough data */
+			            PageAddress = FrameBuf[ISO15693_REQ_ADDR_PARAM];
+                    }
+
+                    if ((FactoryLockBits_Mask & (1 << PageAddress)) || (UserLockBits_Mask & (1 << PageAddress))) {
+                        FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_ERROR;
+                        FrameBuf[ISO15693_ADDR_FLAGS + 1] = ISO15693_RES_ERR_BLK_ALRD_LKD;
+                        ResponseByteCount = 2;
+                    } else {
+                        UserLockBits_Mask |= (1 << PageAddress); /*  */
+                        FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR;
+                        ResponseByteCount = 1;
+                    }
+                }
                 break;
             case STATE_SELECTED:
-                /* TODO: Selected has to be impemented altogether */
+                /* Selected state is not supported by Ti TagIt Standard */
                 break;
 
             case STATE_QUIET: